Recently i found mouse lags in iTunes 8.0.2 and QuickTime 7.5.5. I noticed it first with iTunes, mouse lags appear only if app. is launched (when its closed there is no problems), so i downgraded itunes to v7.7 (from 10.5.4 dvd) and lag is gone. The same i found with QT so i downgraded it also.

Actual problem came from updated graphic drivers in 10.5.6. I reinstalled GeForce* and NVDA* from 10.5.5 and updated iTunes and QT to the latest versions again. Problem gone. Not sure right now what is causing these lags with new graphic drivers.

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Cyclonefr made a post on apple support.

http://discussions.apple.com/thread....35578&#8635578

So more info there

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Mac Inspiron 531 » 10.6.8 • 10.8.0 Legacy Kernel • AMD Athlon 64 X2 5000+ (2.60GHz)
Dell M2N61-AX/nForce 430/MCP61 • 4GB Dual Channel DDR2 667MHz
ALC888 • nVidia GeForce 8600 GT 256 MB
2 x WDC WD5000AAKS 500 GB SATA HDD

Definitely something wrong with drivers. I even tried with my 8800GTS, 320MB, the same thing. Rolled back to 10.5.5 drivers.

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Something strange here. I fixed the issues, though i did nothing particularly big. I was messing with efi strings (with 8800 GTS -320) and tried with new one created with latest EfiStudio v.1.0. I reinstalled 10.5.6Update again.

Right now iTunes, QuickTime and VLC are running at the same time. No mouse lag and no graphical problems at all.

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so the latest version has better hex strings for some of the hardware instead of just the normal addition of new hardware? nice to hear.

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nfoav8or, There was no big difference in efi strings. My previous one was working just great since i installed the system. I was also injecting graphic strings via dsdt, working great, so completely removed device-properties from com.apple.boot. So i am a bit unsure here if it was new string from efistudio or reinstalling 10.5.6 update. Lots of people were complaining about mouse lags in iT/QT with nvidia 8xxx serie but definitely graphic drivers are not broken. Re-installing the update and trying with new string should fix the issue. Worked for me.

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Cyclonefr posted a solution here,
http://forum.insanelymac.com/index.php?showtopic=142056

Seems to be the best one...

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Mac Inspiron 531 » 10.6.8 • 10.8.0 Legacy Kernel • AMD Athlon 64 X2 5000+ (2.60GHz)
Dell M2N61-AX/nForce 430/MCP61 • 4GB Dual Channel DDR2 667MHz
ALC888 • nVidia GeForce 8600 GT 256 MB
2 x WDC WD5000AAKS 500 GB SATA HDD

Yes, could be a good solution. But i didn't downgrade anything.

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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.

It affects some cards from 8xxx series like 8500, 8600, 8800. Didn't affect my 8800 GTS though. Could be the case with your 6800 also. Not to downgrade the drivers just follow the post above (cyclonefr fix) if you updated quicktime/itunes. If you didn't upgrade QT/iT and still have the mouse lag then the cause is something different.

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