Is it a general can't include error, or a open_basedir type of error that you're encountering?
It should be fairly simple to fix in cPanel, if think you would just edit php.ini to turn this setting off. In Plesk you would exit the vhost (belongs somewhere in the user directory) to set it off. Obviously you want to only do this on a per-account basis.
Sorry about not posting a reply. The kind folks at KH helped me track down the problem. My settings were all correct....but they ended up having to [FONT=Verdana, Arial, Helvetica] recompiled Apache and PHP. After that, everything works swell. [/FONT]