It could be a number of things, and most likely the problem is in the registry somewhere.
Try what Tomas_Sweden said as well.
And this m ight seem really dumb to try, but let me explain.
I want you to try 2 different things.
1. Create a new user profile and login to that new account and see if you have any luck.
2. Has the camera been in the same USB port this whole time? I want you to simply use a different USB port.
Now the 2nd option might seem rather odd. But let me explain. I have had a few customers call me and say that their cameras (Not web cam) was not working on their computer and the transfer wizard never came up.
On one of them I had found that Windows simply couldnt install the drivers for it for some odd reason, they where installed and Windows would just say the device failed to load. Uninstalling and reinstalling did nothing. As soon as I plugged it in another USB port Windows then installed it fresh again and everything started working.
On a different customers their camera showed up in the device manager, but again the transfer wizard wouldnt see it. The instance I plugged it into a different usb port Windows had it working again.
When you plug a device into a different USB port Windows treats it as a whole new device and not one it already had installed before. So if something was messed up with the device in Windows before, by plugging it into a different usb port that it hasnt been in yet, Windows will treat it as a brand new device for the system and make the necessary registry changes
So trying a different USB port is always a good option to try.
Shane