I first had installed 0.9.9.11 and added movies, then saw that there is a new version and installed it to a new directory, using (of course after a backup :-) the old database. On the new 0.9.9.12, i got the same problem with "conversion errors" when adding new movies, and i got the same or very similar error message when i started 0.9.9.12 for the first time.
Updating existing entries works without such "conversion error", and i saw another detail on adding new movies: the movies seem to be added to the database with all the details, but in the final step it is not added properly to the list of movies because of this error.
My guess on what goes wrong: the changelog for 0.9.9.12 lists as new feature "Date added and Date modified fields support time", and that might be highly dependend from the country, version of Windows, used language in Windows and used language in PVD. I am using the German version of Vista, but have installed the english PVD, and the Vista system formats are: Date = TT.MM.JJJJ, Time = HH:mm:ss
btw: With Vista, my config file is not in "C:\Documents and Settings\%USERNAME%\Application Data\Personal Video Database\", but "C:\Users\%USERNAME%\AppData\Roaming\Personal Video Database"
At least there is a new IMDB importer which also works on 0.9.9.11: getting one poster now works (although it would be nice to select one of the many pictures; even if done by a separate "IMDB poster import" script), but "aka" is still missing for many movies, and doing cut&paste to get one of the AKAs as title might be done simpler ... but this probably should go into another thread :-)