Green/red screen at startup

Hi,

For the past 3 days whenever I turn my computer on I get a green screen instead of the login screen, once it was red. I have to force a shut down as the restart button doesn't work.

The second time I boot up everything seems to work fine, I turn the pc off and it happens again.

I took a picture of it:http://imageshack.us/photo/my-images/337/20120328124431...

Any ideas what can cause this?

My system is:

Windows 7 64
GTX280
8gb mushkin
Msi p67a-gd53
i5 2500k

thanks,