Ahhh, I doabt that actually. Sorry. Its probably more likly comcast was throttling and when you swapped modem the counter was reset. A cable modem is too dumb to be able to block a port, nevermind dynamically restrict it. It would be like your toaster not toasting wheat, but being fine with white. But besides that, I have used 5101, 5120 and 6120 personally and seeded just fine. Glad you were able to fix it though. ::thumbs up::