Hi, I'm having this problem on the front ans the back end to edit an item.
when you access the editing an item k2 form, and transparent layer stays on top block mouse and cursor access to the editing fields and buttons.
Look at the image for better understanding.

It looks like CSS is not properly loaded or some 3rd party plugin is breaking K2's JS (including the tabs). Check your browser's console for any errors and report them back please.

Thank you for getting back to me.
After I clicked on SAVE, on that page, it went away and has not come back yet.
The console did not show any conflict.

So it was probably a temporary CSS or JS caching issue. Thanks for letting me know.