viewport bug?

This always happens in edit mode after I mark seams.
Can anyone help me fix this?
My PC is a core i7, 8 GB ram and a Quadro 2000.


I never faced this exact problem, but I did have another issue which yielded similar results as seen above (it drove me mad).

To fix my specific issue, I selected all vertices, removed all doubles and then recalculated, hopefully this can help you.

LOL … unfortunately not, but thanks for the help.
This should be something related to my hardware.