Comment 42 for bug 554263

I think this is a bug with uvcvideo how it handles usb devices.

I have the same problem on my desktop with a SYBA SY-CAM63012 usb webcam. I am able to use the webcam with skype after plugging it in, but it stops working at some point and can not be restarted without powering off the entire machine. Soft reboot (restart) does not clear the problem.

I suspect that the usb controller chip on the motherboard shuts down one or more usb ports, and requires a complete power cycle to reset it's internal logic. I will have to test this further.

Acer Veriton M410. AMD Athlon 64 X2 Dual Core Processor 5000+. ATi Radeon HD 4350.
Ubuntu 10.04 LTS, kernel 2.6.32-27-generic-pae (32 bit), xorg radeon driver (NOT flgrx).

This is the dmesg line that indicates the problem.
    ehci_hcd 0000:00:13.5: force halt; handhake f8248024 00004000 00000000 -> -110

Webcam is reported by lsusb as "0ac8:3420 Z-Star Microelectronics Corp." and skype says it is a "Venus USB2.0 Camera"