i posted a thread a while back about similar. Try looking into your wireless connections as if you have auto on a few local connection you may be picking up or trying to connect to it will disconnect you.
i had to always repair or reconnect every 30-60minutes. now i still get it but only a few times a day. Im pretty sure it has something to do with networking and sharing of other devices as this only started when i made my computer able to print from another computer. If not that it is the encryption we put on out network, as this is the only changes made before this problem started for me. (for the encryption to be enabled and working we had to stuff around with the wireless device settings on the PC.....i have a T-sinus stick and the router is T-com sinus DSL, they werent bought as a kit together)