FFXI and Wireless InternetFollow

My brother bought this game and is trying to play with a wireless internet provider. He can create a character and login, he can run around all he wants, chat etc, etc. But for some reason whenever he zones (excluding moghouse) he gets stuck in the downloading data screen and then he gets the server time out message. It generally takes a few min before he can log back in and then he will usually end up at the zone he tried to get to before. When he is playing there is no lag and his S and R numbers are pretty good so it dosn't seem like its a performance issue.

I've opened all the proper ports that FF needs and also contacted his ISP to make sure they don't block any ports. Also thier tech support was useless on the matter. I've tried both with and without a router, I'm pretty much at a loss at what to do now. I know its not his computer because a land DSL or cable line works just fine. Other online games work fine, he's tried playing Guild Wars and Counter strike.

Basically what I'm wondering is if anyone in a similer situation has found a way around this yet, and if anyone can offer any advice.