Every time I went to scan with MS Office Document Imaging for my Canon LIDE 25 under Windows 7 x64 I got the error “Unable to initialize scanner. Check scanner connection and scanner software”.
It appears this is due to the driver installer not modifying the path which the Canon twain driver requires. Follow the instructions at http://weblogs.asp.net/jeffwids/archive/2009/11/02/canon-scanner-unable-to-open-twain-source.aspx and the problem goes away.
Just trying to make it all work... and then stay that way 