Go 510, "Do you wish to connect to Computer"

Hi,
My wife bought me this re-furb unit back in February and until recently everything has been fine. However over the past couple of weeks it has started flashing up the PC connection screen, the "Do you wish to connect to Computer, Yes/No", at seemingly random times while it is on the car dock in my truck. Sometimes the message will disappear on it's own, sometimes I have to press "No" to clear it. After this has happened it also closes down the voice prompts and I have to switch the unit off and re-start it again to get the voice back.
Annoying to say the least. I've tried software updates but it still does it.
Anyone have any ideas what might be causing this and more importantly, what I can do about it !

Cheers

Gary