I've only experienced this problem with MystV and Half-Life 2.
Sometimes when there is rapid movement on the screen, the game pauses for a second or two and then resumes with distorted graphics.
Examples are shown at
http://www.charybdis.dsl.pipex.com/MystV/Scene.jpg
http://www.charybdis.dsl.pipex.com/MystV/Detail1.jpg
http://www.charybdis.dsl.pipex.com/MystV/Detail2.jpg
What I find particularly puzzling is that the problem can only be resolved by rebooting. Restarting the game is not sufficient. This suggests to me that maybe a cached file has been corrupted.
When the PC has got into this state all the DxDiag tests are still passed.
The graphics card is based on nVidia GeForce FX5600 and this problem has persisted through several driver updates.
CPU is Pentium 4; O/S is WinXP Home.
Any ideas would be appreciated.

Suggestions:

1. Correctly install the proper driver for your video chipset as detailed in Myst V: Installing Video Drivers With Win XP.

2. If that doesn't help, re-install EoA from a clean boot as detailed under Installing and Re-Installing EoA, "6. Clean-boot EoA Re-install, Previous Installation" in Myst V: Clean Boot Install/Re-install With Win XP.

And there's also Myst V: Miscellaneous Video Problem Fixes.