I would also like to point that I experienced troubles using ath5k:

Oct 29 06:35:43 portant kernel: [   73.930882] ------------[ cut here ]------------
Oct 29 06:35:43 portant kernel: [   73.930887] WARNING: at /build/buildd/linux-backports-modules-2.6.27-2.6.27/debian/build/build-generic/compat-wireless-2.6/net/mac80211/main.c:232 ieee80211_hw_config+0x9e/0xa0 [lbm_cw_mac80211]()
Oct 29 06:35:43 portant kernel: [   73.930893] Modules linked in: af_packet binfmt_misc ppdev acpi_cpufreq cpufreq_stats cpufreq_userspace cpufreq_powersave cpufreq_ondemand freq_table cpufreq_conservative pci_slot container wmi sbs sbshc iptable_filter ip_tables x_tables parport_pc lp parport joydev snd_hda_intel snd_pcm_oss snd_mixer_oss snd_pcm snd_seq_dummy snd_seq_oss snd_seq_midi snd_rawmidi snd_seq_midi_event snd_seq arc4 ecb crypto_blkcipher evdev psmouse snd_timer snd_seq_device ath5k snd serio_raw pcspkr lbm_cw_mac80211 i2c_piix4 soundcore snd_page_alloc lbm_cw_cfg80211 i2c_core led_class video output fglrx(P) battery ac button shpchp pci_hotplug ext3 jbd mbcache sr_mod cdrom sd_mod crc_t10dif pata_atiixp ata_generic 8139cp sg usb_storage libusual usbhid hid 8139too mii ehci_hcd pata_acpi ahci ohci_hcd libata usbcore scsi_mod dock thermal processor fan fbcon tileblit font bitblit softcursor fuse
Oct 29 06:35:43 portant kernel: [   73.931016] Pid: 2718, comm: ath5k_pci Tainted: P          2.6.27-7-generic #1
Oct 29 06:35:43 portant kernel: [   73.931020] 
Oct 29 06:35:43 portant kernel: [   73.931021] Call Trace:
Oct 29 06:35:43 portant kernel: [   73.931034]  [<ffffffff8024e9b4>] warn_on_slowpath+0x64/0x90
Oct 29 06:35:43 portant kernel: [   73.931047]  [<ffffffffa04a5cef>] ? ath5k_hw_reset+0xf1f/0x1140 [ath5k]
Oct 29 06:35:43 portant kernel: [   73.931056]  [<ffffffff803a73e5>] ? __ratelimit+0xa5/0xf0
Oct 29 06:35:43 portant kernel: [   73.931062]  [<ffffffff80471585>] ? net_ratelimit+0x15/0x20
Oct 29 06:35:43 portant kernel: [   73.931073]  [<ffffffffa04a88c2>] ? ath5k_reset+0x232/0x240 [ath5k]
Oct 29 06:35:44 portant kernel: [   73.931092]  [<ffffffffa044297e>] ieee80211_hw_config+0x9e/0xa0 [lbm_cw_mac80211]
Oct 29 06:35:44 portant kernel: [   73.931113]  [<ffffffffa0447da5>] lbm_cw_ieee80211_scan_completed+0xc5/0x340 [lbm_cw_mac80211]
Oct 29 06:35:44 portant kernel: [   73.931134]  [<ffffffffa0448095>] ieee80211_scan_work+0x75/0x1b0 [lbm_cw_mac80211]
Oct 29 06:35:44 portant kernel: [   73.931154]  [<ffffffffa0448020>] ? ieee80211_scan_work+0x0/0x1b0 [lbm_cw_mac80211]
Oct 29 06:35:44 portant kernel: [   73.931162]  [<ffffffff80262802>] run_workqueue+0xc2/0x1a0
Oct 29 06:35:44 portant kernel: [   73.931167]  [<ffffffff80262b0f>] worker_thread+0xaf/0x130
Oct 29 06:35:44 portant kernel: [   73.931173]  [<ffffffff80267050>] ? autoremove_wake_function+0x0/0x40
Oct 29 06:35:44 portant kernel: [   73.931179]  [<ffffffff80262a60>] ? worker_thread+0x0/0x130
Oct 29 06:35:44 portant kernel: [   73.931184]  [<ffffffff80266c1e>] kthread+0x4e/0x90
Oct 29 06:35:44 portant kernel: [   73.931190]  [<ffffffff80213c99>] child_rip+0xa/0x11
Oct 29 06:35:44 portant kernel: [   73.931194]  [<ffffffff80266bd0>] ? kthread+0x0/0x90
Oct 29 06:35:44 portant kernel: [   73.931198]  [<ffffffff80213c8f>] ? child_rip+0x0/0x11
Oct 29 06:35:44 portant kernel: [   73.931201] 
Oct 29 06:35:44 portant kernel: [   73.931204] ---[ end trace c1b79d714fc3c5e4 ]---
Oct 29 06:35:44 portant kernel: [   73.935516] ------------[ cut here ]------------


The complete part of dmesg regarding to ath5k is in attachment.