Hi:
What model scanner is it and what operating system are you running?
You might want to go to the UMAX site at:
www.umax.com
And go to the support section.
Pull down the articles on uninstalling and re-installing the scanner software and think about doing that.
If you go to Device manager,take a look at your scanner entry and make sure it looks ok(no ? mark,etc)
How is the scanner connected(usb,parallel).Check that connection.
Vistascan gives you an option to test the scanner connection.Have you tried that and what happens.
Did this scanner ever work?
I had a similar problem and went through all the steps above to no avail and ended up having to do a clean install of the operating system.In my case,either a file had been corrupted or the registry was becoming corrupted,this is probably not your case.
Are you having any other flackey problems,like Operations exceptions,etc.