hello.

when i want to go to Media Manager in k2 i got this message " Invalid backend response. Data is not JSON."
Some month ago a topic was resolved my issue. But today when i want to go to this topic i got this message: "Access Denied You do not have permissions to access this page."
the topic that resolved my issue was this:
www.joomlaworks.net/forum/New-to-K2-Ask-here-first!/520-Cant-Browse-Server-invalid-backend-response?limit=12&start=12#1813

even i disabled joomla error reporting according to another topic but steel my problem Remains.

Hello,

Which version of Joomla! and K2 are you using?

I'm Using Joomla! 2.5.27 & K2 2.6.8

Both Joomla! and K2 are out of date.
You need to update Joomla! and patch it since there is a really critical security issue.
Update K2 to 2.6.9 and try again.

PS. the patch is located in joomla.org