D-Link Gaming Woes

My D-Link Router (Model EBR-2310) is really giving me gripes. I have it in a networked with my PC, PS3 and 360. However, when playing games on my PC, you can tell the router's firewall (or maybe something else) is preventing me from playing games I like the most.

For example: I logon to Battlefield 2142, only to find half the servers listed compared to my routerless config. When joining them I usually get the message "Failed to Connect". I try playing Counter Strike Source, only to see that 400 of the 4000 are actually listed. Again, joining them is a pain. Im lucky to find a server that actually lets me join. Sadly, the router seems to have a mind of its own; it only works when it wants to.

Now Ive attempted to configure the D-Link Router to work with gaming. Ive created my own static ip using portfoward.com 's guide, port forwarded all the games that hadn't worked, put my computer into the "DMZ"
(demilitarized zone), unchecked "Enable SPI", configured the DNS to the setting that D-Link has told me AND STILL NO LUCK

My system build:
Dell XPS 400
375 Watt PSU
NVIDIA GeForce 7900GS (256MB)
Intel Pentium Core Duo 820 2.8GHz Processor
Motherboard: Unknown ( Its a Dell one, I know that)
Creative Sound Blaster Audigy SE Sound Card
Intel PRO/1000 PL integrated Network Card

OS: WindowsXP Media Center 2005 SP3
Router: D-Link EBR-2310 B1 (version 2)
Internet Service: AT&T Yahoo! DSL 6.0MBPS UP/ 768KBPS DOWN

*I have the Windows XP SP3 firewall exceptions set for problematic games*

Thank You For Your Help!