Welp, this totally screwed me over today as I spent hours wondering why my Perl script's MySQL insert and update statements weren't working on some tables. If you've recently upgraded to MySQL 5.5, new tables that you create are InnoDB instead of MyISAM, and so AutoCommit must be turned on or you can just do a commit statement after your inserts and updates. FFFFUUUUUU. PHP has AutoCommit turned on by default, evidently, so it is not effected.
Whatever I'm enthused about at the moment ;-p