Forums down, my fault. I deleted cgi-bin
 

I have restored it, but I still get a 500 server error. Any ideas?

Did you do anything else? Because cgi-bin usually contains all CGI scripts, which vBulletin does not use.

I have my forums in www.mysite.com/forum and I tried moving them to www.mysite.com then changed my mind cause a few things were not working. They were working fine again in www.mysite.com/forum so I highlighted most folders in www.mysite.com's root and deleted them, then the forum went down.

Your site is spitting out a 500 internal server error, if one of the php files for vb is gone, you shouldnt get a 500 error page.

Did you make sure all the vbulletin files are there and that the permissions are set correctly on the files?

Could be an issue with the htaccess file

I could agree with dyna here, is apache running as a cgi and the host possibly had something in the cgi-bin dir for your site?

As this isnt a vb issue as this is happening even in your domains root dir.

I checked the .htaccess file and it's still in my domain root. Thanks guys, I'll check that again.

MY htaccess had this in it
I removed that and it works fine. Any idea what happened, if I need to add that, and what it does?

It runs your PHP scripts as CGI. Basically, there is two ways of running PHP for Apache. As an Apache module or as a CGI binary.