Step 1: Check to make sure SLIR works using the query method.
If using the query method works, you know SLIR is working correctly.
Step 2: Check to confirm that the following doesn't work:
If using the method in Step 2 doesn't work, mod_rewrite is to blame.
Step 3: Open your apache httpd.conf file and look for a relevant <Directory> for your website.
Step 4: Restart apache, and you should be good to go!