Video playback distortion

[peterst28]

I just bought a 22" LCD whose native resolution is 1680x1050 and hooks up to my computer via DVI. My video card is a Gigabyte Geforce 6600 GT. The image looks perfectly fine, except for when it plays videos (movie files, DVDs, etc). There's a strange high frequency wave-like distortion for the video itself, but everything else remains unaffected. When I change the resolution to anything below 1600x1200, use the VGA port, use Linux, or plug the monitor into another computer (was running OS X), the problem goes away. Changing drivers or video players does not affect the problem. I think the problem lies with Direct Draw or my video card. When I turn off hardware acceleration on Direct Draw, the problem also goes away, but my video frame rate drops, so that's not an acceptable solution. Anyone have an idea of what I can do? Here's some info about my PC:

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System Information
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Operating System: Windows XP Professional (5.1, Build 2600) Service Pack 2 (2600.xpsp_sp2_gdr.050301-1519)
BIOS: Phoenix - Award WorkstationBIOS v6.00PG
Processor: AMD Athlon(tm) 64 Processor 3200+, MMX, 3DNow, ~2.0GHz
Memory: 1024MB RAM
DirectX Version: DirectX 9.0c (4.09.0000.0904)
Monitor: Chimei CMV 221D

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Display Devices
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Card name: NVIDIA GeForce 6600 GT
Manufacturer: NVIDIA
Chip type: GeForce 6600 GT
DAC type: Integrated RAMDAC
Display Memory: 128.0 MB
Current Mode: 1680 x 1050 (32 bit) (60Hz)
Driver Name: nv4_disp.dll
Driver Version: 6.14.0010.9371 (English)
DDI Version: 9 (or higher)
Driver Attributes: Final Retail
Driver Date/Size: 10/22/2006 12:22:00, 4527488 bytes