I'd suggest looking at
this support thread on the Steam forums, especially the second post.
The first thing to check is that you have DirectX 11 installed on your computer. What version of Windows are you running?
Quote:Operating System: MUST be either Windows Vista (with Service Pack 2) or Windows 7 (with Service Pack 1). The game won't run on XP... Please don't even try 98/95/3.11/dos.
If you
are running DirectX 11, then you need to make sure that your graphics drivers are up-to-date. I'm not sure whether your graphics card meets the minimum specification, maybe someone else can comment on that.
If that doesn't fix the problem then contact support at
Sev2_support@rebellion.co.uk