Red Macroblocks on Import DV Files

Hello everyone.

I'm stumped and I really hope the community out there can help me find the root cause of the following:

* Importing a few minutes of 720x480, SD DV, PA 1.2, 29.97 fps .mpg file from my JVC Everio. File extension was renamed from .MOD to .Mpg. Until recently, I've not had any trouble. Actually, a five minute piece I was working on a few weeks ago did not exhibit this problem. Here's the problem...
* When I scrub the timeline, preview or render, frames throughout the comp will turn some percentage of red macroblocks. It varies from, say, 50% to 100% of the frame and will last from one to five consecutive frames before simply going away and normal video resumes only to reappear a minute or more later on. The comp can simply be one video file or a combo of things.
* They appear in the same spots after repeated launches of AE (CS3).
* The same source file opened in Vegas Pro or played in Windows Media Player shows zero problems.

Seems like the source is corrupted but for the fact that it edits perfectly in Vegas Pro. Maybe my preferences are not set correctly? I've gone through the various Interpet configurations and nothing changes. Tried deleting/re-importing...nope. Reboots, cache purges...nope.

My system is an Intel Core 2 Duo, Vista Home Deluxe, 3GB RAM and plenty of HDD headroom.

Any thoughts on what I may be doing wrong? I'm a rookie so the list is probably extensive.

Thanks!

-Kurt