Wireless keeps dropping off.

Dell XPS, i7, intel wifi-link 1000 BGN, 6Gb RAM, Windows 7 (64bit).

Ok...my computer is the only one at work that keeps getting dropped by the wireless.  It will connect after I reset the modem.....then after anywhere from 10mins to a few hours I will get dropped and all the other computers will still be connected.  My computer will still see the router and show 5 bars....but just says "unable to connect at this time".  I've updated the drivers on my wifi card.  I've done a system restore. I can plug in (like right now) and I get great internet via ethernet.   It's a D-Link DIR-615 router and I'm pretty sure the admin has updated the firmware on it.  PLEASE help....we're on 8 hour stanby with nothing to do, so everyone is sitting watching youtube and skyping and I'm playing Stronghold 1!!!!!!!!!!

Please help.

Jeff