Hi Tim,
a. When was it last working fine?
b. Are you able to use UVC Web Cam on your computer without any issues?
We don’t have any information about Terratec Grabster AV400’s compatibility with windows 7. I would suggest you to contact its manufacturer and check its compatibility with windows 7.
http://www.terratec.net/en/drivers-and-support.html
http://www.terratec.net/en/company.html
You may try installing the drivers for it in windows vista compatibility mode and check if this helps.
Steps to run the Program Compatibility troubleshooter:
1. Open the Program Compatibility troubleshooter by clicking the Start button, and then clicking Control Panel. In the search box, type troubleshooter, and then click Troubleshooting. Under Programs, click Run programs made for previous versions of Windows.
2. Follow the instructions in the troubleshooter.
For more information visit http://windows.microsoft.com/en-us/windows7/Make-older-programs-run-in-this-version-of-Windows
Link to download driver: http://www.terratec.net/en/products/driver/produkte_treiber_en_19925.html
Hope this information is helpful.
Umesh P - Microsoft Support