"Unable to select TWAIN source" - Canon LIDE 25 scanner issue

Hi.  I had been running Windows 7 Ultimate RC, since July.  When I plugged in my scanner, it went and found the correct software (CanoScan Toolbox), and my scanner worked perfectly. 

This weekend I installed Windows 7 Pro.  When I plugged in the same scanner...nothing happened.  So I installed the CanoScan toolbox, using the setup CD that came with the scanner.  I didn't think much of it.  Subsequently, I pushed a button on the scanner, and Windows Fax and Scan opened, and the scanner made a terrible noise.

When I open the CanoScan toolbox, and try to scan, it says "unable to select TWAIN source."  I have tried the troubleshooter, downloaded the driver and the entire CanoScan program (for 64-bit Vista) from Canon's website, and tried many other fixes. 

Any advice would be appreciated.

Thanks.