I believe my ISP has been trying to fob me off. For the past few months I had a problem with my ADSL connection randomly going dead while I was online, but not actually disconnecting. We ruled out everything from the modem, drivers, other hardware and the line. When nothing solved the problem, they told me that AMD Athlon and AthlonXP processors were known to have a 'power regulation issue' with ADSL modems, and that may explain the problem. They advised me to buy a router with its own power supply. Instead, I installed WindowsXP (used W98SE before) and this has solved the problem.
I can't help but wonder though, were they trying to fob me off? I find it hard to believe that the processor was the problem.
If you dont assign an ip address to the nic which used with the pppeo driver, it can cause the problems you described (no connection lost, but the new transfers are stopped). This is a DHCP related problem, assigning an ip will solve it.