Ever since apple released an update for iTunes to support the iPhone, I have been experience a slew of issues when watching video through iTunes.

Issues:
- random pauses in video that resembles video lag.
- unable to watch in full screen mode without getting video drive has recover message
- or worse, a whole bunch of video recover messages followed by the bsod STOP 0x00000124.

Apple initially stated that there was a compatibility issue with nvidia sata. While indeed that may be true (and they are "working" with nvidia on the issue), this problem is far more wide spread. Many people are reporting that this issue is occuring on Intel hardware (q6600 processor) and nvidia video cards (normally 8800 series).

My specific settings are:
Gigabyte P35C-DSR3
Intel quad core q6600
4gig or ocz ram
Nvidia 8800gts 640meg ram by evga
Raptor 80 gig hdd
Vista home premium x64

I run at factor settings with no overclocking.

After much digging I found two working solutions. For those with older systems please go into your bios and look for 32-Bit_Disk_Access. If you have this setting for your hard drive, change this to enabled. It is also recommended that you update your bios before doing this. For those with newer systems there is another bios setting that should be checked. Under advanced settings there should be two settings known as HPET Mode and HPET settings. Essentially you have the option for on/off and 32 or 64 mode. Please make sure that it is enabled and set to 64 (if you have x64 vista). Choose x32 if your running x32 version of vista. If your running Windows xp, it will ignor these settings.

For more information on Hpet see : http://en.wikipedia.org/wiki/High_Precision_Event_Timer

upon changing my settings for HPET from x32 to x64 and rebooting I am now able to switch back and forth from full screen to other video settings in iTunes. I can also alt tab to another application. This is something that I have been able to reproduce on demand until I changed the HPET settings.