Fatal error: Call to a member function load()...

Fatal error: Call to a member function load()...

Dear, webdesigner

I'v received error msg from my website.
I don't know how to solve this error.
Could you help me?

Error Msg. :

Fatal error: Call to a member function load() on a non-object in .../administrator/components/com_content/models/articles.php on line 196

http://www.mybiopark.com/administrator/index.php?option=com_content&view=articles

Fatal error allways occurs In article manager screen, when I choice "select category" combo box.

thanks in advance.

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Aw: Fatal error: Call to a member function load()...

Try disable plugins.

Aw: Fatal error: Call to a member function load()...

Error is corrected after disabling Joomshopping Reward Plugin.

But how can i use "Joomshopping Reward Plugin" without above error?

For reference,
I have 2 domains. www.mybiopark.com and www.misoroman.com
I have a plan that www.mybiopark.com change to www.misoroman.com.
So I purchased Reward plugin for www.misoroman.com domain and for the testing, I installed to www.mybiopark.com.
But I can't setup reward pluin configuration page.
I think that's why this reward plugin's licence key made by using domain info.(www.misoroman.com). Is this right?

Maybe is this error resulted from this situation or not?

Thanks in advance.

Aw: Fatal error: Call to a member function load()...

Install
Reward 1.2.3