I had the same problem with my Toshiba A215. I kept uninstalling and then re-installing the Toshiba webcam program but that did not work. While their program was installed I was unable to use my webcam on Yahoo or Stickam.

My "Imaging" option was also not listed under my devices like it had been before the problem started.

I uninstalled the webcam program again and restarted my computer. I looked in my device list and the driver showed up again!

Though now I don't have a program to use my webcam if I'm not on Yahoo or Stickam, at least it works on something and I'll see what my other options are from here.