Are you using third-party hardware (e.g., AJA, Matrox)?
We've seen this problem before with out-of-date AJA codecs.
Also, I notice that you're using Premiere Pro 5.5.1, not 5.5.2. I recommend choosing Help > Updates and installing the latest bug-fix update.
---------------------------------------------------------------------------------------------------------
Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
---------------------------------------------------------------------------------------------------------