Strange Graphics after booting up

Lately I've been having trouble after starting my Mac.
After a couple of seconds the screen start to make strange graphic errors, blocks of colured lines is running all over the screen and sometimes there is just a lot of lines all over the screen.
Usually it works fine after holding the restart button down and force the computer to reboot. Then it works all day.
The next morning the same thing happens when I start my computer.

I've attached a screen dump that I was able to do this morning.
I have tried checking the system with Tech Tool and repaired permissions, but nothing seems to be wrong.
What could it be? Should I do something or is there something I should do to check what migh be wrong or is there anyone out there who knows what is happening to my computer?
Could it be the Graphic Card?

Please? Anyone?

It might help if you told us what kind of Mac you had.

It's a Mac Pro. Dual-Core Intel Xeon. 2.66 GHz. 8 GB Ram.

To me it sounds a lot like an overheated graphics card. Does it happen after a very intensive computing session, or on a cold boot?

Like I said, it's when I start the computer in the morning. So it's a cold start.

brad62 said:

Like I said, it's when I start the computer in the morning. So it's a cold start.

Click to expand...

It really looks like a bad graphics card or a driver issue. Since the drivers are Apple-supplied and should be automatically updated via Software Update, assuming everything is up-to-date, you've probably got a hardware issue.

Is it under warranty?