this won't exactly solve your issue, but i have the Go 930 which is obviously from the same 'stable' as your 730, and I have no issues whatsoever with mine, connectivity is excellent on Home Premium x64. kind of disputes TomTom's theory.
I'm guessing you have tried all the usual thing's like reinstalling TomTom Home, disconnecting > rebooting > re-connecting, etc?
I guess if the worst comes to the worst you can try reformatting, is that an option to you? At least you know that it should be working, given that I have no issues with mine.