Frequent internet connection errors.. HELP!?!

I'm running an 8-Core MAC pro with OS X 10.6 on my work's network. Awhile back our server went down, and after it was fixed I began having problems with my internet connection. Some days more than others, while browsing the internet I get a connection error in Safari (this also happens in Firefox) telling me I'm not connected to the internet and that I need to check my network connections. We have multiple computers in my office, and mine is the only one that errors out. I have tried switching ethernet ports, network cables, ports in our Cisco switch, using a usb port adapter, reseting Safari, emptying the cache... everything I can possibly think of and nothing has helped. The connection interruption only last around a minute and doesn't always completely knock out my connection, just enough to affect browsing sometimes. It's more hit or miss on my iChat and email. I can access ip addresses like our mail server when it happens, most the time. Does anyone have any idea what the problem may be?

**Please please don't say it is hardware like the motherboard or anything, please be a setting.. wishful thinking here **