Over at vBulletin there's this
New versions of PHP released - upgrade recommended thread
PHP versions 4.3.11 and 5.0.4 have just been released and include fixes for numerous security holes, and a resolution for the performance issue that affects vBulletin as I described
here. We would recommend that all customers upgrade to either 4.3.11 or 5.0.4 at their earliest convenience.
I'd like to hear from PhotoPost developers if a move to PHP 4.3.11 or 5.0.4 is ok to do without breaking their applications.