[Tigga]

Sarge - I have no idea how that could have happened... All you did was modify the URL's in the vB options section? About the best thing I could suggest would be to upload the original, unhacked files to your site and see if that makes a difference. If not, the only other thing I could think of is something you put in one of those fields is causing it. If that's the case, about the only way to fix it would be to manually edit those things in the datastore table in your database.

paratek - I'm about to send you a PM regarding the permissions...
The calendar URL can be fixed by looking in your calendar_smallmonth_header template, finding calendar.php, and adding $vboptions[bburl]/ in front of it.
You can't put php code in any of the custom templates... You can put the code in the adv_index.php file and use the variables in the custom templates though, or you can use vBulletin's conditionals.