[code]substr [/code] - "code" BBCODE doesn't accept the word substr. posting.php crashes with error.

When we try to post the following, the post is not at all accepted and posting.php crashes with 406/404 error codes.

[code]
.......
.....
...
substr
......
....
...
[/code]

This is the error I got:

Not Acceptable

An appropriate representation of the requested resource /posting.php could not be found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.