Ok I am having the weirdest problem. I had the K2 extension being used as a blog for Joomla! and I could use all the frontend abilities (such as add item, edit item, view similar posts). The client want's the frontend ability enabled.

A week later I come back and the 'Add Item' button is gone. Instead, I get this error message replacing it:
Strict Standards: Declaration of JParameter::loadSetupFile() should be compatible with JRegistry::loadSetupFile() in /home/shisutah/public_html/libraries/joomla/html/parameter.php on line 512

I've checked everywhere, and no-one seems to understand why this is happening and suggests to just turn off error reporting. Turning off error reporting does not fix the problem. I want this fixed since my front end 'add item' function is gone. Any useful help or explanation on what this error actually is would be appreciated.

Hello Brenton,

Strict Standards: is not an error and should not affect your site's functionality.
If you can't turn off error reporting through Joomla! 's config you should contact your hosting provider.

In the meantime you should also check if you are using K2's and Joomla!'s latest version and if your overrides are up to date.