Part of screen went black after iTunes update and playing video games, After

[mayhone1]

Ok guys never had this problem before but part of my iMac's screen went black and the black parts were moving around, again I never had this problem before and it happened shortly after I installed the iTunes update and while I was playing Plants vs. Zombies. I had to hold the button to restart and decided to use time machine to go back to a previous version, it's been a few days and it hasn't done it yet, but I am freaking out because I don't have the money to replace this for the next few months, should I worry, any suggestions on what to do and have anyone else gone through this?

Thanks,

Mayhone!

 

[mayhone1]

anyone have this happen, please I still need some input...