g5 games i can't get into them.

i play g5 games and when i try to play them the blue g5 screen comes up and then it locks up. i can't get out of it a lot of the time it just stays on that one screen. then out of nowhere it will play like normal but only for a couple hours a day and messes up for the other 20 hours a day + or-. i play 9 diff. games and they are all doing the same thing. whats up?

:)