Hi Tom, thanks for responding.
Here are my system specs: Mac Pro 2×3 ghz Quad-Core intel, 8GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.7.5, Premiere 6.0, AE 11.0.0.378. Graid storage connected via eSATA
Codec is prores 442 (which is what the clips were shot in) 1920×1080 @ 29.97fps. Attached are my sequence settings as well. FYI on the last timeline I finalized, I uped the Video previews resolution to ProRes HQ and still had this rendering problem. Only replacing the clips solved the issue.
Thanks,
Michaelle

Mac Pro 2×3 ghz Quad-Core intel, 8GB RAM, ATI Radeon HD 5770 1024 MB, OS 10.7.5, Premiere 6.0, AE 11.0.0.378. Graid storage connected via eSATA