Disabling autosuspend on usbcore on 2.6.22-8-generic on a Gutsy install just resulted in the following warnings within dmesg and no resolution of the black scan problem with a Canoscan LiDE 20:
Bus 004 Device 003: ID 04a9:220d Canon, Inc. CanoScan N670U/N676U/LiDE 20

[   23.178531] usb 2-1: configuration #1 chosen from 1 choice
[   23.199413] WARNING: at /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/core/driver.c:1192 usb_autopm_do_device()
[   23.199421]  [<f886e116>] usb_autopm_do_device+0xf6/0x100 [usbcore]
[   23.199442]  [<f886e486>] usb_suspend_both+0x1c6/0x270 [usbcore]
[   23.199459]  [<f886e0c8>] usb_autopm_do_device+0xa8/0x100 [usbcore]
[   23.199473]  [<f8870fd9>] usb_create_sysfs_intf_files+0x69/0xa0 [usbcore]
[   23.199489]  [<f886ce31>] usb_set_configuration+0x2c1/0x4f0 [usbcore]
[   23.199505]  [<f8874d0d>] generic_probe+0x16d/0x250 [usbcore]
[   23.199521]  [<f886eb23>] usb_probe_device+0x33/0x40 [usbcore]
[   23.199535]  [<c025fa9e>] driver_probe_device+0x8e/0x190
[   23.199544]  [<c02eff23>] klist_next+0x53/0xa0
[   23.199549]  [<c025ed54>] bus_for_each_drv+0x44/0x70
[   23.199554]  [<c025fc66>] device_attach+0x86/0x90
[   23.199558]  [<c025fba0>] __device_attach+0x0/0x10
[   23.199562]  [<c025ecbd>] bus_attach_device+0x4d/0xa0
[   23.199566]  [<c025f109>] bus_add_device+0x129/0x160
[   23.199571]  [<c025d98f>] device_add+0x49f/0x570
[   23.199576]  [<f8868281>] usb_new_device+0x81/0x100 [usbcore]
[   23.199591]  [<f8868f5e>] hub_thread+0x78e/0xc30 [usbcore]
[   23.199604]  [<c02f087a>] schedule+0x2ca/0x890
[   23.199610]  [<c013bd00>] autoremove_wake_function+0x0/0x50
[   23.199616]  [<f88687d0>] hub_thread+0x0/0xc30 [usbcore]
[   23.199629]  [<c013ba42>] kthread+0x42/0x70
[   23.199633]  [<c013ba00>] kthread+0x0/0x70
[   23.199637]  [<c0105487>] kernel_thread_helper+0x7/0x10
[   23.199642]  =======================
[   23.634675] WARNING: at /build/buildd/linux-source-2.6.22-2.6.22/drivers/usb/core/driver.c:1192 usb_autopm_do_device()
[   23.634686]  [<f886e116>] usb_autopm_do_device+0xf6/0x100 [usbcore]
[   23.634710]  [<f886e486>] usb_suspend_both+0x1c6/0x270 [usbcore]
[   23.634727]  [<f886e0c8>] usb_autopm_do_device+0xa8/0x100 [usbcore]
[   23.634741]  [<f8870fd9>] usb_create_sysfs_intf_files+0x69/0xa0 [usbcore]
[   23.634758]  [<f886ce31>] usb_set_configuration+0x2c1/0x4f0 [usbcore]
[   23.634774]  [<f8874d0d>] generic_probe+0x16d/0x250 [usbcore]
[   23.634792]  [<f886eb23>] usb_probe_device+0x33/0x40 [usbcore]
[   23.634806]  [<c025fa9e>] driver_probe_device+0x8e/0x190
[   23.634814]  [<c02eff23>] klist_next+0x53/0xa0
[   23.634820]  [<c025ed54>] bus_for_each_drv+0x44/0x70
[   23.634825]  [<c025fc66>] device_attach+0x86/0x90
[   23.634829]  [<c025fba0>] __device_attach+0x0/0x10
[   23.634834]  [<c025ecbd>] bus_attach_device+0x4d/0xa0
[   23.634838]  [<c025f109>] bus_add_device+0x129/0x160
[   23.634843]  [<c025d98f>] device_add+0x49f/0x570
[   23.634849]  [<f8868281>] usb_new_device+0x81/0x100 [usbcore]
[   23.634865]  [<f8868f5e>] hub_thread+0x78e/0xc30 [usbcore]
[   23.634878]  [<c02f087a>] schedule+0x2ca/0x890
[   23.634884]  [<c013bd00>] autoremove_wake_function+0x0/0x50
[   23.634892]  [<f88687d0>] hub_thread+0x0/0xc30 [usbcore]
[   23.634905]  [<c013ba42>] kthread+0x42/0x70
[   23.634909]  [<c013ba00>] kthread+0x0/0x70
[   23.634913]  [<c0105487>] kernel_thread_helper+0x7/0x10
[   23.634918]  =======================