downloads fail following triple play install

I have been a long comcast internet and cable TV customer. Today I upgraded to the triple play soloution to consolidate bills and save some money on phone bills. My internet was working perfectly yesterday before the technition came out. He swapped my existing cable modem with a VOIP model to accomodate the new phone service. since this time I am unable to download. I am running XP SP3 over IE7 and for purposes of testing have unplugged my wireless router and am directly connected to the modem. I am able to surf, open my mail, etc. If I attempt to download a file it appears to work fine for about the first megabyte, but then simply stops. Not hanging, but stops downloading. Eventually gives an error of something like "connection to the server has been reset" I have called comcast many times today. They continuously tell me that everything is fine and working properly and that if I am seeing an issue that it must be a Microsoft issue, but everything worked fine an hour prior to my install .. that dog does not hunt ...

I have deinstalled my firewall, swapped ethernet cables, tried different PCs, tried to download from many different websites, reset the modem a number of times, etc. Not sure what to do next. I was a senior server engineer for many years. I know how to troubleshoot an issue.

This has blown out my whole day and night and it is still not resolved

thank you,