AT&T DSL Time Out.. Every Other ISP Works..

I have 2 business DSL lines at work with (formally SBC) AT&T. We use a linksys (dual-port, but disabled) and a D-Link router on basic DSL modems.

I run a php script that does a few things in the background that takes roughly 15 - 55 minutes to complete. When I click on the button to open the php script, firefox basically gives the hour glass until it finishes.

The problem is.. ANYWHERE besides our office when I click on the php script it works find. It finishes up in like I said.. 15 - 55 minutes. But for some reason (on any computer in the office.. windows and linux) I get a server time-out message after 12 minutes.

I even hooked up 1 windows machine and 1 linux server directly to the DSL modem (both got their on IP Addresses on different Class-C blocks) and it still times out.

I am curious how to even begin to investigate why it times out at 12 minutes. Do you think this is a specific DSL AT&T problem?

I've had 5 friends of mine try the script and every single one of them was able to run it without any problems. Like I said.. works 100% of the time on my home connection. But once I get into work.. 10-12 minutes... "server time out".. but the server is up.. no problems on the connection.