My drive disconnected earlier as I was playing music off of it with mpd, and would not come back online until I rebooted my computer. Turning the drive off and on again, and plugging it back into the usb port failed to get it working. Only after a reboot did it work again. I noticed a few things in my /var/log/messages that I hadn't seen before. Usually, I just get the first four lines of what I've reproduced below. I'm not sure if what is below is related to mpd or related to the drive, so apologies in advance if this post isn't helpful to the discussion. The details for this drive are given in post #47.

Feb  4 00:10:34 tosh kernel: [29023.505128] usb 1-3: USB disconnect, address 2
Feb  4 00:10:39 tosh kernel: [29028.016064] scsi 4:0:0:0: [sdb] Unhandled error code
Feb  4 00:10:39 tosh kernel: [29028.016073] scsi 4:0:0:0: [sdb] Result: hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK
Feb  4 00:10:39 tosh kernel: [29028.016083] scsi 4:0:0:0: [sdb] CDB: Read(10): 28 00 08 2c 10 4f 00 00 20 00
Feb  4 00:10:39 tosh kernel: [29028.017279] ------------[ cut here ]------------
Feb  4 00:10:39 tosh kernel: [29028.017294] WARNING: at /build/buildd/linux-2.6.35/fs/buffer.c:1151 mark_buffer_dirty+0x70/0x90()
Feb  4 00:10:39 tosh kernel: [29028.017301] Hardware name: 00000000000000000000
Feb  4 00:10:39 tosh kernel: [29028.017305] Modules linked in: usb_storage aes_i586 aes_generic lib80211_crypt_ccmp binfmt_misc parport_pc ppdev snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_seq_midi pcmcia joydev snd_rawmidi i915 drm_kms_helper snd_seq_midi_event snd_seq drm psmouse intel_agp snd_timer snd_seq_device snd agpgart yenta_socket pcmcia_rsrc ipw2200 i2c_algo_bit soundcore snd_page_alloc serio_raw video pcmcia_core output tifm_7xx1 tifm_core libipw cfg80211 lib80211 lp parport 8139too firewire_ohci sdhci_pci 8139cp firewire_core sdhci led_class crc_itu_t mii
Feb  4 00:10:39 tosh kernel: [29028.017405] Pid: 19814, comm: mpd Not tainted 2.6.35-25-generic #44-Ubuntu
Feb  4 00:10:39 tosh kernel: [29028.017411] Call Trace:
Feb  4 00:10:39 tosh kernel: [29028.017425]  [<c014ad42>] warn_slowpath_common+0x72/0xa0
Feb  4 00:10:39 tosh kernel: [29028.017434]  [<c023d7f0>] ? mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017442]  [<c023d7f0>] ? mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017452]  [<c014ad92>] warn_slowpath_null+0x22/0x30
Feb  4 00:10:39 tosh kernel: [29028.017460]  [<c023d7f0>] mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017470]  [<c0281f9a>] T.1020+0x4a/0x70
Feb  4 00:10:39 tosh kernel: [29028.017479]  [<c028202b>] ext3_handle_error+0x6b/0xc0
Feb  4 00:10:39 tosh kernel: [29028.017487]  [<c0281009>] ? ext3_msg+0x49/0x50
Feb  4 00:10:39 tosh kernel: [29028.017496]  [<c02820d4>] __ext3_std_error+0x54/0x90
Feb  4 00:10:39 tosh kernel: [29028.017505]  [<c0279732>] ext3_reserve_inode_write+0x42/0x90
Feb  4 00:10:39 tosh kernel: [29028.017514]  [<c02797ab>] ext3_mark_inode_dirty+0x2b/0x50
Feb  4 00:10:39 tosh kernel: [29028.017523]  [<c02798fe>] ext3_dirty_inode+0x4e/0x80
Feb  4 00:10:39 tosh kernel: [29028.017533]  [<c0237561>] __mark_inode_dirty+0x31/0x190
Feb  4 00:10:39 tosh kernel: [29028.017542]  [<c022cd6a>] touch_atime+0xea/0x130
Feb  4 00:10:39 tosh kernel: [29028.017552]  [<c01daf9a>] T.924+0x3da/0x480
Feb  4 00:10:39 tosh kernel: [29028.017563]  [<c021726f>] ? __dentry_open+0x18f/0x280
Feb  4 00:10:39 tosh kernel: [29028.017573]  [<c01db10b>] generic_file_aio_read+0xcb/0x2a0
Feb  4 00:10:39 tosh kernel: [29028.017584]  [<c0230d1f>] ? mntput_no_expire+0x1f/0xd0
Feb  4 00:10:39 tosh kernel: [29028.017594]  [<c0218a04>] do_sync_read+0xa4/0xe0
Feb  4 00:10:39 tosh kernel: [29028.017603]  [<c01f730b>] ? vma_link+0x6b/0xa0
Feb  4 00:10:39 tosh kernel: [29028.017616]  [<c032ed56>] ? apparmor_file_permission+0x16/0x20
Feb  4 00:10:39 tosh kernel: [29028.017628]  [<c03031b4>] ? security_file_permission+0x14/0x20
Feb  4 00:10:39 tosh kernel: [29028.017637]  [<c0218aa2>] ? rw_verify_area+0x62/0xd0
Feb  4 00:10:39 tosh kernel: [29028.017646]  [<c02192cf>] vfs_read+0x9f/0x190
Feb  4 00:10:39 tosh kernel: [29028.017655]  [<c0218960>] ? do_sync_read+0x0/0xe0
Feb  4 00:10:39 tosh kernel: [29028.017664]  [<c0219402>] sys_read+0x42/0x70
Feb  4 00:10:39 tosh kernel: [29028.017675]  [<c05ca5d4>] syscall_call+0x7/0xb
Feb  4 00:10:39 tosh kernel: [29028.017685]  [<c05c0000>] ? amd_check_l3_disable+0xc0/0x1be
Feb  4 00:10:39 tosh kernel: [29028.017691] ---[ end trace dd779cb5b7d83cb2 ]---
Feb  4 00:12:51 tosh kernel: [29160.260067] khubd         D f5f44c54     0    21      2 0x00000000
Feb  4 00:12:51 tosh kernel: [29160.260079]  f712fd50 00000046 00000000 f5f44c54 f62b6000 f5f44c4c c08c4700 c08c4700
Feb  4 00:12:51 tosh kernel: [29160.260096]  9359adac 00001a65 c08c4700 c08c4700 00000000 00001a65 f63d0e00 c08c4700
Feb  4 00:12:51 tosh kernel: [29160.260112]  c08c4700 f7138000 00000001 f5853fc8 7fffffff f5853fcc f712fdb4 c05c8895
Feb  4 00:12:51 tosh kernel: [29160.260128] Call Trace:
Feb  4 00:12:51 tosh kernel: [29160.260148]  [<c05c8895>] schedule_timeout+0x1a5/0x270
Feb  4 00:12:51 tosh kernel: [29160.260157]  [<c05c7f0a>] ? schedule+0x37a/0x7a0
Feb  4 00:12:51 tosh kernel: [29160.260170]  [<c013a224>] ? enqueue_entity+0x174/0x200
Feb  4 00:12:51 tosh kernel: [29160.260180]  [<c05c8536>] wait_for_common+0xa6/0x120
Feb  4 00:12:51 tosh kernel: [29160.260191]  [<c0142e10>] ? default_wake_function+0x0/0x20
Feb  4 00:12:51 tosh kernel: [29160.260202]  [<c05c8687>] wait_for_completion+0x17/0x20
Feb  4 00:12:51 tosh kernel: [29160.260212]  [<c0165c2f>] kthread_stop+0x3f/0xb0
Feb  4 00:12:51 tosh kernel: [29160.260227]  [<f9f19fa7>] release_everything+0x27/0xa0 [usb_storage]
Feb  4 00:12:51 tosh kernel: [29160.260239]  [<f9f1a03f>] usb_stor_disconnect+0x1f/0x30 [usb_storage]
Feb  4 00:12:51 tosh kernel: [29160.260250]  [<c04763c0>] usb_unbind_interface+0x40/0x150
Feb  4 00:12:51 tosh kernel: [29160.260260]  [<c0400d11>] __device_release_driver+0x51/0xb0
Feb  4 00:12:51 tosh kernel: [29160.260268]  [<c0400e35>] device_release_driver+0x25/0x40
Feb  4 00:12:51 tosh kernel: [29160.260277]  [<c04000bb>] bus_remove_device+0x7b/0xa0
Feb  4 00:12:51 tosh kernel: [29160.260287]  [<c03fe207>] device_del+0xf7/0x180
Feb  4 00:12:51 tosh kernel: [29160.260296]  [<c04730a3>] usb_disable_device+0x63/0x110
Feb  4 00:12:51 tosh kernel: [29160.260305]  [<c046d4ee>] usb_disconnect+0xae/0x140
Feb  4 00:12:51 tosh kernel: [29160.260314]  [<c046da9a>] hub_port_connect_change+0x8a/0x8f0
Feb  4 00:12:51 tosh kernel: [29160.260323]  [<c0473ca3>] ? usb_control_msg+0xd3/0x130
Feb  4 00:12:51 tosh kernel: [29160.260333]  [<c0460100>] ? ppp_start_xmit+0x20/0x190
Feb  4 00:12:51 tosh kernel: [29160.260342]  [<c046f270>] hub_events+0x2b0/0x4f0
Feb  4 00:12:51 tosh kernel: [29160.260351]  [<c016606f>] ? finish_wait+0x4f/0x70
Feb  4 00:12:51 tosh kernel: [29160.260359]  [<c046f4ea>] hub_thread+0x3a/0x140
Feb  4 00:12:51 tosh kernel: [29160.260368]  [<c0165f00>] ? autoremove_wake_function+0x0/0x50
Feb  4 00:12:51 tosh kernel: [29160.260376]  [<c046f4b0>] ? hub_thread+0x0/0x140
Feb  4 00:12:51 tosh kernel: [29160.260384]  [<c0165ad4>] kthread+0x74/0x80
Feb  4 00:12:51 tosh kernel: [29160.260392]  [<c0165a60>] ? kthread+0x0/0x80
Feb  4 00:12:51 tosh kernel: [29160.260401]  [<c010363e>] kernel_thread_helper+0x6/0x10

The corresponding logs for /var/log/syslog are:

Feb  4 00:10:34 tosh kernel: [29023.505128] usb 1-3: USB disconnect, address 2
Feb  4 00:10:39 tosh kernel: [29028.016064] scsi 4:0:0:0: [sdb] Unhandled error code
Feb  4 00:10:39 tosh kernel: [29028.016073] scsi 4:0:0:0: [sdb] Result: hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK
Feb  4 00:10:39 tosh kernel: [29028.016083] scsi 4:0:0:0: [sdb] CDB: Read(10): 28 00 08 2c 10 4f 00 00 20 00
Feb  4 00:10:39 tosh kernel: [29028.016107] end_request: I/O error, dev sdb, sector 137105487
Feb  4 00:10:39 tosh kernel: [29028.016378] EXT3-fs error (device sdb1): ext3_get_inode_loc: unable to read inode block - inode=8536075, block=17072130
Feb  4 00:10:39 tosh kernel: [29028.016839] EXT3-fs (sdb1): error in ext3_reserve_inode_write: IO failure
Feb  4 00:10:39 tosh kernel: [29028.017279] ------------[ cut here ]------------
Feb  4 00:10:39 tosh kernel: [29028.017294] WARNING: at /build/buildd/linux-2.6.35/fs/buffer.c:1151 mark_buffer_dirty+0x70/0x90()
Feb  4 00:10:39 tosh kernel: [29028.017301] Hardware name: 00000000000000000000
Feb  4 00:10:39 tosh kernel: [29028.017305] Modules linked in: usb_storage aes_i586 aes_generic lib80211_crypt_ccmp binfmt_misc parport_pc ppdev snd_intel8x0 snd_ac97_codec ac97_bus snd_pcm snd_seq_midi pcmcia joydev snd_rawmidi i915 drm_kms_helper snd_seq_midi_event snd_seq drm psmouse intel_agp snd_timer snd_seq_device snd agpgart yenta_socket pcmcia_rsrc ipw2200 i2c_algo_bit soundcore snd_page_alloc serio_raw video pcmcia_core output tifm_7xx1 tifm_core libipw cfg80211 lib80211 lp parport 8139too firewire_ohci sdhci_pci 8139cp firewire_core sdhci led_class crc_itu_t mii
Feb  4 00:10:39 tosh kernel: [29028.017405] Pid: 19814, comm: mpd Not tainted 2.6.35-25-generic #44-Ubuntu
Feb  4 00:10:39 tosh kernel: [29028.017411] Call Trace:
Feb  4 00:10:39 tosh kernel: [29028.017425]  [<c014ad42>] warn_slowpath_common+0x72/0xa0
Feb  4 00:10:39 tosh kernel: [29028.017434]  [<c023d7f0>] ? mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017442]  [<c023d7f0>] ? mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017452]  [<c014ad92>] warn_slowpath_null+0x22/0x30
Feb  4 00:10:39 tosh kernel: [29028.017460]  [<c023d7f0>] mark_buffer_dirty+0x70/0x90
Feb  4 00:10:39 tosh kernel: [29028.017470]  [<c0281f9a>] T.1020+0x4a/0x70
Feb  4 00:10:39 tosh kernel: [29028.017479]  [<c028202b>] ext3_handle_error+0x6b/0xc0
Feb  4 00:10:39 tosh kernel: [29028.017487]  [<c0281009>] ? ext3_msg+0x49/0x50
Feb  4 00:10:39 tosh kernel: [29028.017496]  [<c02820d4>] __ext3_std_error+0x54/0x90
Feb  4 00:10:39 tosh kernel: [29028.017505]  [<c0279732>] ext3_reserve_inode_write+0x42/0x90
Feb  4 00:10:39 tosh kernel: [29028.017514]  [<c02797ab>] ext3_mark_inode_dirty+0x2b/0x50
Feb  4 00:10:39 tosh kernel: [29028.017523]  [<c02798fe>] ext3_dirty_inode+0x4e/0x80
Feb  4 00:10:39 tosh kernel: [29028.017533]  [<c0237561>] __mark_inode_dirty+0x31/0x190
Feb  4 00:10:39 tosh kernel: [29028.017542]  [<c022cd6a>] touch_atime+0xea/0x130
Feb  4 00:10:39 tosh kernel: [29028.017552]  [<c01daf9a>] T.924+0x3da/0x480
Feb  4 00:10:39 tosh kernel: [29028.017563]  [<c021726f>] ? __dentry_open+0x18f/0x280
Feb  4 00:10:39 tosh kernel: [29028.017573]  [<c01db10b>] generic_file_aio_read+0xcb/0x2a0
Feb  4 00:10:39 tosh kernel: [29028.017584]  [<c0230d1f>] ? mntput_no_expire+0x1f/0xd0
Feb  4 00:10:39 tosh kernel: [29028.017594]  [<c0218a04>] do_sync_read+0xa4/0xe0
Feb  4 00:10:39 tosh kernel: [29028.017603]  [<c01f730b>] ? vma_link+0x6b/0xa0
Feb  4 00:10:39 tosh kernel: [29028.017616]  [<c032ed56>] ? apparmor_file_permission+0x16/0x20
Feb  4 00:10:39 tosh kernel: [29028.017628]  [<c03031b4>] ? security_file_permission+0x14/0x20
Feb  4 00:10:39 tosh kernel: [29028.017637]  [<c0218aa2>] ? rw_verify_area+0x62/0xd0
Feb  4 00:10:39 tosh kernel: [29028.017646]  [<c02192cf>] vfs_read+0x9f/0x190
Feb  4 00:10:39 tosh kernel: [29028.017655]  [<c0218960>] ? do_sync_read+0x0/0xe0
Feb  4 00:10:39 tosh kernel: [29028.017664]  [<c0219402>] sys_read+0x42/0x70
Feb  4 00:10:39 tosh kernel: [29028.017675]  [<c05ca5d4>] syscall_call+0x7/0xb
Feb  4 00:10:39 tosh kernel: [29028.017685]  [<c05c0000>] ? amd_check_l3_disable+0xc0/0x1be
Feb  4 00:10:39 tosh kernel: [29028.017691] ---[ end trace dd779cb5b7d83cb2 ]---
Feb  4 00:10:39 tosh kernel: [29028.017897] journal_bmap: journal block not found at offset 1769 on sdb1
Feb  4 00:10:39 tosh kernel: [29028.017905] Aborting journal on device sdb1.
Feb  4 00:10:39 tosh kernel: [29028.017948] EXT3-fs (sdb1): error: ext3_put_super: Couldn't clean up the journal
Feb  4 00:10:39 tosh kernel: [29028.017957] EXT3-fs (sdb1): error: remounting filesystem read-only
Feb  4 00:12:51 tosh kernel: [29160.260051] INFO: task khubd:21 blocked for more than 120 seconds.
Feb  4 00:12:51 tosh kernel: [29160.260060] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Feb  4 00:12:51 tosh kernel: [29160.260067] khubd         D f5f44c54     0    21      2 0x00000000
Feb  4 00:12:51 tosh kernel: [29160.260079]  f712fd50 00000046 00000000 f5f44c54 f62b6000 f5f44c4c c08c4700 c08c4700
Feb  4 00:12:51 tosh kernel: [29160.260096]  9359adac 00001a65 c08c4700 c08c4700 00000000 00001a65 f63d0e00 c08c4700
Feb  4 00:12:51 tosh kernel: [29160.260112]  c08c4700 f7138000 00000001 f5853fc8 7fffffff f5853fcc f712fdb4 c05c8895
Feb  4 00:12:51 tosh kernel: [29160.260128] Call Trace:
Feb  4 00:12:51 tosh kernel: [29160.260148]  [<c05c8895>] schedule_timeout+0x1a5/0x270
Feb  4 00:12:51 tosh kernel: [29160.260157]  [<c05c7f0a>] ? schedule+0x37a/0x7a0
Feb  4 00:12:51 tosh kernel: [29160.260170]  [<c013a224>] ? enqueue_entity+0x174/0x200
Feb  4 00:12:51 tosh kernel: [29160.260180]  [<c05c8536>] wait_for_common+0xa6/0x120
Feb  4 00:12:51 tosh kernel: [29160.260191]  [<c0142e10>] ? default_wake_function+0x0/0x20
Feb  4 00:12:51 tosh kernel: [29160.260202]  [<c05c8687>] wait_for_completion+0x17/0x20
Feb  4 00:12:51 tosh kernel: [29160.260212]  [<c0165c2f>] kthread_stop+0x3f/0xb0
Feb  4 00:12:51 tosh kernel: [29160.260227]  [<f9f19fa7>] release_everything+0x27/0xa0 [usb_storage]
Feb  4 00:12:51 tosh kernel: [29160.260239]  [<f9f1a03f>] usb_stor_disconnect+0x1f/0x30 [usb_storage]
Feb  4 00:12:51 tosh kernel: [29160.260250]  [<c04763c0>] usb_unbind_interface+0x40/0x150
Feb  4 00:12:51 tosh kernel: [29160.260260]  [<c0400d11>] __device_release_driver+0x51/0xb0
Feb  4 00:12:51 tosh kernel: [29160.260268]  [<c0400e35>] device_release_driver+0x25/0x40
Feb  4 00:12:51 tosh kernel: [29160.260277]  [<c04000bb>] bus_remove_device+0x7b/0xa0
Feb  4 00:12:51 tosh kernel: [29160.260287]  [<c03fe207>] device_del+0xf7/0x180
Feb  4 00:12:51 tosh kernel: [29160.260296]  [<c04730a3>] usb_disable_device+0x63/0x110
Feb  4 00:12:51 tosh kernel: [29160.260305]  [<c046d4ee>] usb_disconnect+0xae/0x140
Feb  4 00:12:51 tosh kernel: [29160.260314]  [<c046da9a>] hub_port_connect_change+0x8a/0x8f0
Feb  4 00:12:51 tosh kernel: [29160.260323]  [<c0473ca3>] ? usb_control_msg+0xd3/0x130
Feb  4 00:12:51 tosh kernel: [29160.260333]  [<c0460100>] ? ppp_start_xmit+0x20/0x190
Feb  4 00:12:51 tosh kernel: [29160.260342]  [<c046f270>] hub_events+0x2b0/0x4f0
Feb  4 00:12:51 tosh kernel: [29160.260351]  [<c016606f>] ? finish_wait+0x4f/0x70
Feb  4 00:12:51 tosh kernel: [29160.260359]  [<c046f4ea>] hub_thread+0x3a/0x140
Feb  4 00:12:51 tosh kernel: [29160.260368]  [<c0165f00>] ? autoremove_wake_function+0x0/0x50
Feb  4 00:12:51 tosh kernel: [29160.260376]  [<c046f4b0>] ? hub_thread+0x0/0x140
Feb  4 00:12:51 tosh kernel: [29160.260384]  [<c0165ad4>] kthread+0x74/0x80
Feb  4 00:12:51 tosh kernel: [29160.260392]  [<c0165a60>] ? kthread+0x0/0x80
Feb  4 00:12:51 tosh kernel: [29160.260401]  [<c010363e>] kernel_thread_helper+0x6/0x10

I hope this helps in some way. I'm a complete newbie when it comes to interpreting logs.