LaserSoft Imaging

I have a Canon 8400f that works great. about a month ago I purchased Silverfast Ai Version 6447r. It worked Great for a couple of weeks. all of a sudden It gives me errors like (an error occured at the start of the scanning process. cannot start the Scanner)

I tried uninstalling, reinstalling. it will maybe scan 1 picture then same error. Tried deleting the pref file and copying the Wnaspi32.dll to the silverfast file
Tried installing on 4 other computers I have Same results. Canon software works fine
I have sent request for support to laserSoft 3 times in the past Week and a half. No response from anyone.

Can anyone Help Me Please
thanks

I just upgraded to 6.5.0r3. I still am getting errors (an error occurred a the start of the scannig process. Cannot send Command "Set Window" ) and cannot start the scanner. Just what can I do to fix this
thanks