Thanks for this quick tutorial jakiman. Buffer size did not work on my main card, so I had to lower it to 2432 though. Some utc love coming your way!
Actually I had a hunch that if it is my main card, it is probably out of memory, due to some visual stuff. I tuned down all the visual things in windows 7 and 2560 is now a go!
Woohoo. I'm glad you got it sorted and also glad I was of some help.

Thank you for the UTC! You were the first and only one to tip me for it...