Re: Blank Pages Or HTTP 500 Internal Server Errors.
It also appears that you have your forum software installed directly to the root of your web-space and NOT in its OWN folder such as /forum or whatever?
AND, if you have doing been anything that affects the .htaccess file - such as adding http permissions like hotlinking, there's a good chance that you have broken it.
So delete or rename the .htaccess file to something else - and try some more.
500 errors are common to bad CHMOD permission settings, which includes an .htaccess file that has been screwed up.
GOOGLE and learn something.
