Some games dont work

Hi, I tried to run Silkroad Online and my system doesnt seem to let it play, I start up the game and then all I see is a picture like I would be in game, but It shows frozen desktop and after that I can see mouse cursor has changed to the game one. Similar problem is with BF heroes, the game engine loads up and its all black, I hear a sound of error, but I cant do anything about it. Mouse cursor also changes. I suspect a same problem. I can play COD 4 an Counter-Strike source on max settings. BTW Runes of Magic install doesnt seem to load up in task manager I can see it.

My specs:
Intel Quad 2.4Ghz Q8200
Nvidia GeForce 9800GT Newest drivers
Value Ram DDR2 4GB
Failry good screen.

Thx 4 reading guys.

might be a corrupted memory module...last time i got blue screens of death, it was a stick of ram that was bad...try running some sort of memory checker like Memtest or something...

BUMP

Do what Ahslan says for a start, either run Memtest or run with just one stick in at a time.
This seems to be a problem with online games so check your internet connection and that your AV software is not interfering with it, Gamespy or Punkbuster.
If you do not have any AV software or a decent firewall installed your should at least download either Spybot or Adaware and seep the system for problems.
And check your running processes for anything that looks wrong.