Join the club, keeps happening to my mother, and bugs the hell out of me when i am round their.
I called Virgin, they said a bunch of, well rubbish. Nothing solved as of yet...
However, i can add this to the equation, well for me...
PC = Always connected
LAPTOP With Dell Wifi (Broadcom i think) = Always connected
LAPTOP with intel = Drops frequently
Cant figure it out... I recon its an intel flaw with the router (DLINK)... Taking my Belkin round next week to see if this solves the issue