Scrolling diagonal lines on monitor

[innervision]

Hey all,

I noticed on my monitor there are scrolling diagonal lines at various locations, depending on the colors being displayed. They seem to show up around shades of gray, or dark hues of other colors.

System specs:
System: Dell XPS 420
Processor: Intel Core 2 Duo E8400
Video: ATI Radeon 3870
Monitor: Acer AL2216W bd

If any other information is required to diagnose the problem, please let me know.

Thanks a lot for any help.