As the game is still in pre-alpha it has many bugs. Post them here.
Bug Reports Sticky
Do you have the latest video drivers?
No.Where i can get the latest video drivers?
What GPU do you have? Only those that support DX10 and up are supported.
It isn't always the drivers. It is sometimes just the file missing. I have a new PC that I got this week and it didn't come with it but everything is updated.