Twain Driver not loaded

Tricky problem with the twain driver on this system. Its looks to be all there but when you go to use any of the scanner software a twain error appears. I uninstalled the Canon N670U software then on trying to reinstall it with the CD it tells me the Twain driver needs to be installed. In device manager on WIN XP pro I tested the scanner in Imaging Devices and all was OK in there. So I used the twain driver uninstaller from Canon to remove everything. Downloaded the latest drivers for this scanner that also had the twain drivers with it. Installed these and still had the same problem when I went to install the software. Telling me to install the Twain drivers?