Using BT headset and GPS satnav at the same time?

[Guest jcostantino]

I have a problem when I use TomTom and my BT headset at the same time. My position/heading jump around and speed up/slow down randomly when I'm speaking on the headset but not when it's turned on but no call is being made. The GPS receiver is also Bluetooth but it's a cheap one.

If it matters, I'm using a Wizard and this happens at bout 195 and 247 mhz so it isn't a speed issue. I think it could be caused by too much bluetooth bandwidth being taken up by the headset. I just wanted to know if anyone else had seen this before.