Thanks for sending the requesting info. It looks like your server has Suhosin installed for additional security. I believe one of the "get" request settings is causing the issue. The get request string created by this plugin is rather long and probably exceeding the default settings found under Suhosin.
You can create a php.ini file in your root directory and change some of the get variables found here: http://www.hardened-php.net/suhosin/configuration.html#suhosin.get.max_array_depth
For example you should be able to create the php.ini file and add:
This is currently set to 256 so I am effectively quadrupling it. I'm not certain this is the exact option that needs to be tweaked and it may be a combination of the "get" options to make it work.
Once you make a change, view the phpinfo.php file and verify that the setting has been reflected in under the Suhosin section (search for the option name on the page)
Sorry I don't have a definite answer but maybe someone else out there may have an idea.
Let me know if this works for you.