Edit post gives 406 error if changes are made

http://amolpatil2k.x10hosting.com/blog/

Very strange behavior indeed.

Click on edit post. Don’t make any changes. Click on save and everything happens normally.

On the other hand if I

Click on edit post. Make changes and click on save, I get a 406, whatever that means.

Not Acceptable

An appropriate representation of the requested resource /blog/wp-admin/post.php could not be found on this server.
Apache/2.2.9 (Unix) mod_ssl/2.2.9 OpenSSL/0.9.8b mod_mono/1.9 mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 Server at amolpatil2k.x10hosting.com Port 80