G4 displays not not waking up after sleep

I have a problem with G4 D.A., my displays are not turning back on after sleep mode. If the displays are in mirror mode they wont turn back on, If mirroring is off they work fine. I am using a radeon 9600pro vid card. I just upgraded to os 10.5 from os 10.3. It worked fine with 10.3 but not with 10.5. I looked on ati web sight for upgrades but could not find anything. Is there anything I can do or do I have to just live with it?

Thanks for any advice.