I've run across a weird issue that I was wondering if anyone had seen before. We run a custom version of Ubuntu 10.04 at work and we've been testing some software that uses webcams recently, which 90% of the time works great but we've had a crash event on two separate pieces of hardware with quite different configurations which basically disables the in-built webcam completely.
I've run through checking lsmod, lsusb, dmesg to see if the device or module appears at all (it doesn't), the block reference in /dev disappears completely and for all intensive purposes the webcam is gone. We then ran through a series of tests culminating in a fresh install of Ubuntu 10.04 LTS with no tweaks which once again couldn't find the webcam, the only way we could get it to appear was to install XP, autodetect it, then swap back into Ubuntu which would then acknowledge it.
My initial thoughts run to something to do with power control (I used to have an Aspire One, and if you used the Wifi power off switch a similar thing would happen), but I have no idea whether I'm on the right track or where to start looking to try resolve that one.
Any thoughts about what could cause a device to become apparently 'powered off' from the USB bus, and why it would require Windows would be much appreciated.
Additional: We can actually get the cam to come back up if the machine has function keys for enable/disable webcam, but we've still not isolated what triggers it.