I have a similar problem. After I had successfully connected my TomTom 910 to my Intel iMac several times, TomTom Home crashed repeatedly, and the iMac would no longer recognize the TomTom drive as connected. When I wrote TomTom support to ask for help, this was their response:
"We would like to thank you for your message to TomTom Customer Support. I understand that you are experiencing problems with your TomTom GO 910 not being recognized by the computer. We are more than glad to assist you!
The reason why I asked you for that information is because we have detected a compatibility issue with the Intel Core Duo processor, it uses a different architecture than the G4/G5 Mac processors. This architecture (i386) is the normal PC architecture so the Mac OS had to be completely redesigned or hybridized to work with it. Because of this reason is that we cannot guarantee that TomTom HOME will work free of problems. Our developers are already working in a solution for this issue.
We apologize for any inconvenience caused."
To date, more than a month later, they have neither contacted me with a fix nor put any warning on their website.