I made some more experiments and when I changed the WiFi AP channel from 11 to 1 the connection improved. No more disconnects, but I think it still did slow down the connecion, and occasionally caused it to pause downloading. Therefore I'm pretty sure the Bluetooth and WiFi do interfere with each others...

Also both of them are exactly at the same frequency band: 2.40-2.48GHz. Bluetooth should be hopping between the whole band, while WiFi is more constant at the set frequency band.

Anybody seen this behavior in your N800 or 770? If you turn on your bluetooth radio does it degrage your WiFi connection?