Connectivity Issue: Can't Connect to One Site and No Idea Why

Since I moved into my new apartment and got AT&T U-verse I've had some issues FTPing into my webhost. Basically the client would access the site and I could browse around for a bit before it timed out and the site went down for 15-30 minutes before returning to normal. I could then rinse and repeat.

I've got an Airport Extreme hooked up to the U-verse modem and I could sometimes get thru if I set the client to passive mode and used the built-in wireless on the AT&T modem. Then on Friday or Saturday everything went dead and I haven't been able to access the site (front end or the hosting server through the online portal). I checked with the hosting company and they said I should have no problems (and I can access it from other networks), but I'm still unable to connect. Here's [the traceroute information](http://cl.ly/LMbt).

I know just about nothing about networking so I've mostly been blindingly trying things and hoping they'd work or the issue would resolve itself. No luck, although I did realize the U-verse modem has a firewall that blocks all connections by default, which probably explains the FTP issues.