Win7 64 -- Counter Strike Source Crash

Everytime I try to run Counter Strike Source, it crashes. Very very frustrating, especially since I play CS:S for league play and tournaments--it is hard to get on and practice/play matches when you can't launch the game. I will do my best to describe my system, and all the symptoms, and steps I have taken so far. Sorry if it gets a bit wordy--I am at my wits end, and I just need help.

Win7 Ultimate 64
Dual Monitors (1920x1080 & 1280x1024)
E8400 @ 4.05ghz
eVGA 790i SLI FTW Digital PWM
eVGA 9800GTX+
4Gb Corsair DDR3 @ 1600mhz
640Gb WD Caviar Black
500Gb WD External
Creative X-fi Xtremegamer Fatal1ty
600W PSU

Using Steam to install and run Counter Strike Source.

Essentially, I cannot play CSS at all. I click to open the game, both screens flash a few times--the CSS background comes up, then I get the world famous "HL2.exe has caused an error" etc etc. I let it search for a cause, it never finds one. I have installed the latest video drivers, as well as the latest nForce drivers--but have had better luck with my network when using the Windows drivers (per my research online, I have found that many nVidia chipset users have had to revert to Windows drivers for their Network device as well).

I figured it could be a bad video driver, since the screens would flicker upon launch--so I updated to the newest forceware without any help.

I wondered perhaps if it is a network issue between my router and Win7 so I upgraded the firmware on the router, no help.

Finally, I believe I have nailed it down to an error when launching 1920x1080 into CS:S from Win7. I set my default resolution in Win7 to 1440x900, and CS:S would launch, then I could manually change my resolution to 1920x1080 in-game and it would run. I was able to play for a short while--then the game crashed again. Needless to say, it is rather hard to play a game that wont run. My system is more than capable of running source (source engine is not very demanding), I can average well into the 200-300 fps range with 16xAF and 4xAA but for some reason the resolution is causing me all this trouble.

I believe there is a way to force a certain resolution upon launching source--but the instructions I have found so far have been vague at best.

Anyone that has had similar problems or has any other troubleshooting ideas, please feel free to reply--as I said, I'm about at my wits end . Thanks guys!

Has anyone else encountered an error like this?