John,
When dealing with trying to work a project between different builds, releases, and versions of a given software, there is frequently a compatibility problem. The conventional advice (and wisdom) has been once a project is started in one build or version it is best completed in that one.
What I would do depends on what format you are trying to edit. Best and most reliable would be to do the re-install as suggested being sure you have a clean registry after uninstalling and before re-installing.
Then go back to your original media and begin the edit anew. Could be a bit of a PITA but I find when I've had to do that I pretty much remember enough of what I did and it's gone far faster than I dreaded (and this was with other software).
Approach #2 is if you edited in standard def. Clean off or delete material in the title track and the music track and render to a full screen AVI. Then in build 1915 import that AVI as new media, have PD7 detect scenes and when that is done drag 'n drop the scenes to the timeline in order. Add new titles on the title track and redo the music on the music track.
If you use the magic music (SmartSound) seriously consider acquiring their standalone music program. Right now the Express Tracks Edition is free with any music purchase from their albums and for very limited time they still offer 6 new albums for $49.95. I just snapped up Scoring Suites at that price even though I already have the Scoring Edition software.
This package will let you score to specific lengths and export to a file you can drag 'n drop to the music track of almost any video editing package. And all of their newer disks are multilayer giving you tremendous flexibility in muting or reducing specific instrument layers.