Im having the same problem.
I have to use google maps to get a gps lock then use IGO 8 and that works great, however I would like to be able to use TomTom or Garmin so that I can use the GPS feture if I dont have access to data.
I know that people on this board are having success using TomTom and Garmin. If you could tell us what steps, settings, radio as well as the rom you have used to make it work it would be greatly appreciated.