So, when I tried to load my site, this comes up: I have no idea how to solve this, could someone direct me in hte right way?
500 = Someone made a boo-boo Are you running a server off your PC or do you have a host? If you have a host contact them and let them fix it. If you are hosting yourself, what kind of setup do you have?
i hit this same problem only a week or two ago and contacted the vbulletin support people. they told me it's almost always got to do with modified code (e.g. installs hacks) or with the skin. i told them that it is impossible since i've been running my forum for a while now and the problem suddenly appeared when i try creating a thread in a specific forum. in any event, after some serious trouble-shooting, found out that it was because i was cutting and pasting text from another source into the edit field to be part of my post. the copied text had some 'special characters' that vb couldn't process. could it be the same problem as yours? the error message is identical though.
I think you should check your .httacess plus try to chmod file to 777 and if it still gives error then contact your host Saad