I'm using the latest stable Processing on WinXP(32bit).
I have an analog CCTV camera connected via USB using this thing:
http://www.encore-usa.com/us/taxonomy/term/491/all. The drivers are properly installed, and everything recognizes the camera. Other programs are able to view the camera's feed just fine.
Processing, however, just gives me a blank image, as though no frames are ever available. I've tried my own code plus several of the Capture examples.