Random Posting error
 

I'm using 3.8 and occasionally I get this error when I am trying to post either a new topic, or a response. I know that others have been getting it as well:

Forbidden
You don't have permission to access /community/newreply.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/1.3.41 Server at [mywebsitehere] Port 80

Anyone have any idea what could be causing this?

- The file doesn't exist, check your files
- mod_security or Suhosin is installed on your server and is blocking the request. Contact your host.
- You have a modification installed that causes this: Disable all modifications and try again.

Thanks! To be honest, I reckon it's being caused by a mod. I'll try disabling them to work it out. Cheers.