Later addition. I have discovered that the scanner is working fine using different software. I tried ArcSoft PhotoStudio using "acquire" on the file menu and it worked just fine, both platen and ADF. I seems that it is just the MP Navigator softwar...
I am having exactly the same problem and Ive tried all the uninstalling and reinstalling. I have also tried email questions and got no solution and not even acknowledgement that it is a known problem. Do I actually have to buy a new scanner?