Users Module Settings Problem
 

Hey guys, just wondering if anyone can help me.

I'm having a strange problem when I click on "Update Settings" in the Settings tab of the Users Module (Control Panel > Administration > User Administration > Settings), whereby it gives me the following page:

Forbidden

You don't have permission to access /index.php on this server.

Does anyone have any idea why this maybe happening? I'm not having this problem with any other module, and I can create Users with no problems - It's just when I try to "Update Settings".

Any help would be greatly appreciated, cheers,
Luke