Originally posted by Quikiki:

Title says it all really.

-Reinstalled
-Verified Cache
-Definitely have system requirements

Just press start, launches a window, closes the window then closes the game.

Anyone else?

When you reinstalled, did you uninstall AND delete the install folder? Steam uninstalls do not remove mod files.

What does "definitely" mean to you? In my experience, people that know they have sufficient hardware usually list that hardware.

Have you tried being of anti-virus or other security dictates software is interfering?