I know it doesn't take much to pull off FPSC building but I'd like
to think its your video card. ATI cards do some weird stuff at times.
I used to use ATI fanaticly and after having games running
with a horrible amount of bugs and tears (on my HD 6850) I switched
to Nvidia. I have a laptop with a ATI Mobility 4250 in it and it can
run FPSC quite well but they have different drivers then your card.
All I can say is try updating your drivers if you haven't as well.
It can work wonders for you. If that fails, switch to Nvidia if
you can. I made the switch and all my problems went away.
AMD Phenom II X6 3.2Ghz, 8GB DDR3 Extreme RAM,
ASUS M4N98TD EVO Motherboard, Nvidia 560 Ti 1GB DDR5