jamesrt:ubergeeknz: I would theorise that it's changing the channel due to interference.
It'd be interesting for someone affected to use a tool such as InSSIDer To see what channel is in use and confirm if it is changing when this happens...
Actually, I did have a look using the WiFi Analysis tool I had installed on my Galaxy S, and as far as I could tell, my Genius was always using the bottom-end of the spectrum (around channel 1 or 2) - there was one other wireless network in range, and that always seemed to be set around channel 9 or so.
Having said that, I am using DECT phones; but I was under the impression that they used a different part of the spectrum. Can DECT collide with WiFi channels? I hadn't noticed any correlation of dropout and phone use.
There didn't seem to be a relationship between dropout and use of microwave over either!
DECT shouldn't interfere, unless it's 2.4Ghz DECT in which case, yes, it will definitely interfere (from experience!)
Microwaves seem to be fine. They are pretty well shielded and I think the frequency is slightly different.