I have only recently added K2 to my site which previously was built on Joomla 2.5 plus CB. I have implemented items and k2 categories and used this to add comments and tags to some of my blogs and it is very impressive.
A slight problem is that I also added some extra fields to one category. it works fine in items that i create using the back end admin but when I then edit the item on the front end not only does the extra field tab not appear but the extra fields disappear when I save the changes to the item.
My editor is JoomlaCK 5 on front and back end.

Hi. Are you getting any javascript errors when you change the category?

No, it all a
Pears good, article saves but extra fields are blanked.

Sorted. I had show extra fields disabled on front end edit and for some reason this doesnt just not show the tab it deletes the text. turning show extra fields on solved the problem.