Re: Fatal error: Call to undefined function: build_datastore()
I'd say that your problem is the older version of vB3 (which is very insecure, btw). I suggest you upgrade ASAP.
vBulletin 3.0.0 or higher.
PHP 4.1.2 or higher (Safe Mode MUST be turned OFF!).
MySQL 3.23 or higher is recommended.
GD library (2.0+ is recommended) or ImageMagick.