MODs, if you feel this should be moved, feel free.
I have three Pis stacked, each serving a different purpose. One of them is running an owncloud server an motion, with an attached webcam - Microsoft (spit) VX3000 I think.
It works fine, for w while, but then loses the camera, and the only solution is to reboot. Then it works fine for a while, and loses it again.
A while can be up to 5 - 6 hours.
I can buy a different cam if needs be, but what might cause this.
The Pi only boots /boot from the SDCard - rootfs is on an NFS drive, so it isn't an SD issue.