When I edit an item in the fontend, I see the normal editor and the tabs (images, Media, Extra Fields, etc.). So thats good. But than I see the items undernieth again? I disabled Jquery, because it's already loaded with another module. It was enabled earlier, and than it looked even uglier.

Hope someones inderstands :unsure:

I am having the same problem. Every section on the popup window (for both adding and editing items) repeats twice... add image, add attachment, the text editor even shows twice, though one shows without any text styling controls. Even the sidebar shows up twice when the "Default state for the item form sidebar" is set to "Shown."

Sometimes, if the popup is open for longer than a few minutes, it goes completely blank and firefox keeps trying to load from static.getclicky.com.

I am using K2 2.5.4 and Joomla 1.5.15 (an old version, but I am hesitant to update since I believe the previous developer didn't use overrides).

I have not seen this before. I would at least try to backup with akeeba, install the site on localhost, and upgrade there to 1.5.25 and try that. If The previous dev did not use overrides, then copy the contents of com_k2/templates/default to an override directory, rename it and give it a try. If they hacked the core...your in for a headach. 1.5.25 is not secure any longer, and 1.5.25 will reach end of live soon. Best to start working on the testing now

I have upgraded the Joomla version to 1.5.25 on my localhost without issue.

But it still seems like the frontend editor popup doubles all fields. Whats worse, is now the popup almost immediately goes blank, tries loading from static.getclicky.com, and will not close.