This usually happens after one or two hour's use. Since I haven't been able to find a corresponding process in the task manager (at least not one I'm comfortable trying)I have to restart the whole system in order to get my connection back which is, to say the least, very frustrating.
I'm running Windows XP - service pack 3.
The laptop itself is a refurb so I can't be 100% sure of the hardware.
Using a different browser doesn't seem to have any effect either way.