I have this problem, I've forwarded my port in my router, I've OPENED the port in COMODO, but still it happens. When I do the port check for uTorrent, it passes half the time. Whenever this happens, the total download speed in uTorrent is limited to 30 kB/s. I'm using a US Robotics USR8054 router, a TrendNET TEW-444UB USB wireless adapter, and a Speedstream 5200 modem. I've forwarded the port in the router, opened the port in the FIREWALL of the router, and opened the port in Comodo. I've also tried disabling Comodo and changing the port but nothing helps. This doesn't happen all the time, but it is very irritating when it does.I would suspect the router.
You could check if a firmware update is available for it.
Before attempting an update be sure to check what the update actually does. If the changes doesn't sound like they could fix your problem it is probably not worth updating.
Also be sure to read the instructions on firmware updating carefully. Doing it wrong could turn your router in to a pretty expensive paper weight.I've had the LATEST firmware for the router for at least 2 years now, they haven't released anything new.Try bypassing the router and connect directly to the modem... the test should tell you whether the router is at fault or not.