I'm using TomTom6 with my 680. I have the Globalsat BT359W. when it works, its great but I have the following issue which is really annoying:

1/ Switch on Tomtom and then the BT359 and it connects most of the time.
2/ I receive a call or I briefly switch to my contacts whilst in tomtom and then go back to Tomtom, most fo the time, it does not connect again and I have to switch bluetooth off completely for a few minutes and then reconnect again.

this is very annoying whilst on route and you lose the tomtom for that period.

is this normal?