I know

and I have searched high and low for some sort of port forwarding info on your modem...
The general consensus is it is a modem only and not a modem/router, so it can't be port forwarded...
I even registered at the port forwarding site so I could find out some info and I'm still waiting for my password and until they send it, I can't post...
(I registered yesterday)
I did find a thread from a forum that suggested that it wasn't the modem that was blocking a torrent program they where using but a hidden firewall within the computer from an old work security program, when they uninstalled it everything was fine...
I recall you mentioning that your brother knew a bit about what was installed on your comp..Maybe ask him if he knows of any program that could be causing this...
I'm at a loss....try registering at
PortForward.com Forum you may have better luck getting your password sent to you...