I have a HP Pavilion dv9715nr entertainment laptop which has done the same thing. Webcam does not exist, but there is an unknown USB device, error code 43. I know it is not a Toshiba but I have seen the same problem all over the web in forums about many different makes.
To cut to the chase, I have finally found that HP don't support Windows 7 on my model.

They have a list of models that they will do updates for to ensure Windows 7 compatibility, mine is not on it.
It actually specifically refers to this in the HP support section that webcams may not even be recognized, that is my (and yours too I think) problem. Device manager can't see any imaging device and lists it as an unknown usb root controller device.
Driver is 6.1.7601.17586 , 21-June-2006- port #2 hub #3. (which means nothing to me)
End result is 'no video device detected' even after scan for hardware changes, disabled/uninstalled device and restarted and so on, nothing has worked.
I am hoping perhaps some kind of 3rd party may have whatever it will take (
driver, BIOS update??) to get it going with Windows 7, because HP basically say use recovery and go back to vista. I'd prefer to stay with Windows 7 myself.
So does anyone know how we can get these suckers going if the manufacturer says tough cheese?