Hi people, sorry to butt in. I'm a little desperate now since I'm having the same issue - can't see K2 Items or Categories in the backend. The only way to see them is to delete the browsers cookies for the site everytime you want to change something in K2. Obviously I can't hand it over to the client like this.
I have the same issue on Mac Firefox , Safari and Chrome and Windows Firefox, Chrome and Explorer - K2 is finished unless there is a solution very soon!
Please let me know how you resolved it?