What can I do?

[Waltz5]

Hello, when playing graal sometimes my computer just freezes up. Or the screen blinks and I can play, but no one else moves, then a blue error screen goes up.

What can contribute to this? Is it just really bad server lag?
Btw this has happend ever since I've had Graal.
I have a cable modem but it sure doesn't seem like it.
I was thinking my Video card.. I think I have a real crappy one. Can this contribute or what else?

PS: I didn't know what forum to post this in so I just posted it here in the most frequent visited forum.

Thanks for your help in advance.