I have gotten very good results by using
strra ttn7.916.9192_vga_black tweaked.cab (
http://www.megaupload.com/?d=NDLQX1MN)
and
GpsModDriver_151.cab
you need to go into GPS settings in Tomtom and set as other bluetooth on com3. It's just interpolated positioning, but it works very well. I have no more issues with Tomtom now. Good luck!