When attempting to upgrade from phpBB2 to phpBB3 I needed to be able to convert my old database to my new one the convert script throws a large amount of errors and the resulting forums are not functional. The error appears to be that the convert script is attempting to perform an INSERT on the postgresql database and use a "" as the null value which is not permitted in postgresql.

Screenshot here: http://www.shsu.edu/~ajm023/phpbb3convertFAIL.png