An appropriate representation of the requested resourc

[Mum]

My forum has been working fine for months. All of a sudden i get this error when trying to post a new thread.

Not Acceptable
An appropriate representation of the requested resource /forums/newthread.php could not be found on this server.

I have checked via FTP and that file is there, so what can i do to fix this?

[Dismounted]

What hacks have you installed?

[Mum]

It was this that caused it http://www.vbulletin.com/forum/showthread.php?t=197290