nano + bluetooth gives problems

Hi,

I'm having problems using bluetooth on my nano as a GPS source for navigation.
Basically it works but the nano freezes every now and then for up to 1,5 to 2 minutes.
In that case the leds stay off or on and the nano does not respond to the switch/button anymore. The navigation device looses the connection with the nano.
When the leds start to blink again the BT connection is also reestablished and the navigation continues. But as this sometimes occurs every minute this setup is not usable for navigational purposes.

I have tried several setups using:
two differnt nano's (one two years old, the other a few months)
an oudie running SYM
a android phone running either nano config tool or XCSoar
An serial conection on my laptop using the SSP BT profile

I have tested several combinations of the hw above while driving to work but also during a flight.
It is completely unclear when the nano decides to freeze.
I have had one or two occasions that the nano kept on working for quite a long time ( 1 hour) and then suddenly decides to go faulty again.

Once the nano is in a bad mode it doesn't matter if there is a Bluetooth device connected or not (I even turned off the phone and oudie). When BT is turned on on the nano then it will hang every now and then. When BT is turned off there is no problem and the nano work flawlessly.
When BT is on but the nano is not moving/logging the problem also won't occur.

Oddly (but fortunately) the nano keeps on logging when it is in this faulty mode and the flight(drive) is stored as a single continous igc file.

I have tried to reset the nano (via the pinhole) and that seems to solve the problem for a while but within half an hour or so the problem will be back.

I have mailed my findings (and log/igc files) to lxnav but al they (can) say is that they are investigating the problem (?)

Has anyone else seen this problem/behaviour?

Stephan