Bnet: Connection Issues

[seph ir oth]

As posted in the Battle.net forums, found here:

I have Battle.net login errors for all classic Battle.net games (Starcraft, Warcraft III, Diablo II). Starcraft II is fine.

It attempts to connect and times out.

My computer can play on classic Battle.net if I am on another network, so it seems to be a network issue. I initially contacted Blizzard support via email and they suggested to contact my ISP.

My ISP reminded me to open ports on my computer and router. They are open, and to be doubly sure I have no issues with the router, I plugged my computer directly into the modem. I still couldn't connect. Beyond that, my ISP claims that they do not block any ports whatsoever (I asked specifically about the 6112-6119 range classic Battle.net uses).

A "technician" that visited from my ISP suggested that I should try altering my MTU (max transmission unit) to a lower amount (originally 1500). I tried 1300 and 1400 to no avail.

Does anyone have any idea why I might not be able to connect to Battle.net beyond what I've stated? I can do practically anything and everything else with my ISP's connection (Age of Empires, XBox 360 stuff, etc).

Anyone got an idea? It's bugging me