We use virtual user home directory paths so you can get errors when trying to setup search engine friendly URLs. If can be fixed very easy. Edit your .htaccess file and one simple line to it:
Make sure this line is placed before all the other rules (on the first line of .htaccess file). That's it. Now your rewrite rules will be working fine.
Note: if you are installing your script to some subdirectory such as www.yoursite.com/forum/, you have to place RewriteBase /forum line to the .htaccess file which is located in public_html/forum directory.