Glad you found a way to get the revised project completed.
And for the confirmation that you were dynamically linking PR CS5.5 with EN CS5.1.
If you have a project set to Bluray (in the project settings; not the build panel), and revert, it reverts the bluray transcode, but not the DVD. Is the project set to bluray by any chance? I see the transcode choice greyed out for DVD if it is still transcoded after the Bluray reverts.