Spreadsheet - error 500 with registered users in Joomla

Hi - i have setup a couple of spreadsheets. when logged into the website as an super admin the spreadsheets view ok. but when i try to view them as a registered user i get the following error message

HTTP Error 500 (Internal Server Error): An unexpected condition was encountered while the server was attempting to fulfill the request.

And when i look at my PHP Error logs i see these messages

[code][04-May-2013 23:49:10 Pacific/Auckland] PHP Notice: Undefined variable: params in \site\templates\default_template\library\Artx\Content\SingleArticle.php on line 51

[04-May-2013 23:49:10 Pacific/Auckland] PHP Fatal error: Call to a member function get() on a non-object in \site\default_templates\template\library\Artx\Content\SingleArticle.php on line 51

Does anyone have any ideas how i can fix this?


is it possible that this error was caused by something else?
I also tried to find files with errors, but I can’t see them into default joomla package.

I don’t think so as these errors only started after I setup the spreadsheet on the server. It appears the messages have stopped coming through after the mysql and apache services were restarted.

I will keep an eye on it and see if any other messages appear.