Hi,
When I played this game I had this exact problem.
For some months I had the luxury of having 2 ISP

I normaly used my HomePNA 1MB ISP, but now and then I got this problem, described in this thread.
Then I would boot and switch to the other ISP, that only was 128kb, but the game worked fine.
Once I even tested to switch back to the 1MB ISP, to see if the problem realy was with the ISP, and it was.
I did a tracert to start to ping the routers, to see wich one had varience in responce time. In my case my ISP router (default gateway) had un even responce times from maybe 10ms - 3000ms
I also had this problem before having 2 ISP. Then it some times dissapeare if I rebooted the PC. Maybe I got connected in a different ATM or what its called
But I can say with 100% surtenty that a) I can't spell and 2) it was in my case an ISP problem.