Comment 2 for bug 293259

I have found the solution to this problem, as described by Jean-Francois Moine, who is I believe the maintainer of v4l/gspca in the kernel:
http://bugzilla.kernel.org/show_bug.cgi?id=11920

what I had to do was simply uncheck the zc0301 driver when compiling gspca (http://moinejf.free.fr/gspca_README.txt) using make config. Compiling it with the zc0301 driver was not putting the vend:prod into the gspca module, as described by Moine, and so was preventing the gspca driver from detecting the camera. In Hardy 8.04 it was enough to unload the zc0301 module.

The entry in the bugzilla kernel talks about the sn9c102 driver, that has to be removed, so it seems it applies to more than one model/type of webcams.

I hope this is helpful to some people and that it might get fixed soon so that others can use their webcams again.