Chttpexception - Unable To Resolve The Request "site/error".

Hello,

I'm trying to debug a strange error we're having when trying to access the backend of our website:

When we goto backend.php we receive this error:

CHttpException
Unable to resolve the request "site/error".

We are running a Linux machine, using PHP 5.3.1

The only thing I can think of is that it could be htaccess or permissions related. Here's what's in our Htaccess file:

-------

AddDefaultCharset utf-8

Options +FollowSymLinks
IndexIgnore */*
RewriteEngine on

RewriteRule ^backend backend.php

# If a directory or a file exists, use it directly.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# Otherwise forward it to index.php.
RewriteRule . index.php
RewriteRule \.svn/ - [F]
-------

Any help would be greatly appreciated, so far googling hasn't helped...

Thanks!