how did you downgrade to 10.5.5 drivers? i am currently on iPC 10.5.6 with a fresh install as last time i installed graphics drivers, i got mouse lag and it made the system unusable. i have an xfx nvidia 6800gt card (10de:0402] (rev a1) and i'm unsure which drivers i should be using on 10.5.6 to avoid these mouse lags. i've installed steermouse just in case but apart from that i have a fresh system? i might add that it wasn't just using itunes and quicktime that i had lag, i had lag pretty much all the time after rebooting with the graphics drivers installed.