Telnet/IRC ports Blocked?

A couple of weeks ago, I've noticed that the network would spontaneously halt. Usually, webpages are fine, but both telnet and IRC have been disabled, it seems. We usually have three computers on the network: 2 desktops and one laptop with a third PC that sometimes substitutes for the second. My cousin's desktop has yet to experience the problems while the Powerbook (on a wireless connection) sometimes loses its ability to use Telnet. The last PC (which is interchanged with my new computer, which has yet to maintain a stable connection) often suffers the most. It seems that the signal is sent out; ZoneAlarm catches that. However, nothing gets through. My cousin's pretty sure he set up the router correctly; all was fine until I tried putting my computer on the network.

Proggies that don't seem to work: Telnet (on 6112, as instructed by Blizzard, though it seems that no one there has an answer to my problem), IRC (6667-7000), WarCraft IIII (6112-6119)

All three desktops are on Windows XP Pro. Mine is the only one with a firewall, ZoneAlarm, but I only installed that two days ago and the problem's existed before that was installed. The router we use is a Linksys WRT54G.

BTW, I don't have access to the router settings, so it may be tough to gauge those. However, because stuff seems to work completely fine on my cousin's comp and not mine, I wonder if it's my computer instead.