I think I may have made a mistake upgrading one of my sites to 2.7.0 because I was using an Additional Categories plugin. Right now we have completely lost the ability to save anything in K2. I am thinking that I might need to roll back to web site to before the upgrade. Any advice?

Try completely clearing your browser cache and history.
I have had this exact same problem on one of my sites. My browser was caching the old K2 version. The fix above worked for me.

Hi, I gonna use this as I have a similar issue.

It's a fresh install with K2 version 2.7.0
PHP version 5.6.18

When I had an extra field in a K2 category (from Associated "Extra Fields Group")
It becomes impossible to update or add a new item under this category!

It doesn't save and an image appear as you can see below

http://imgur.com/y1Usbox

So just for your information I did download a K2 version 2.6.9 and install it over and it looks to work :)
But it means I can not run the lastest version 2.7.0 right?

Hello,

This has been resolved
github.com/getk2/k2/commit/6cff7526e292321479113783d5d2ea80ae7752a1

You can either use the latest DEV version, github.com/getk2/k2/archive/master.zip or you can apply the patch in the commit's URL I sent you.

Thank you so much, I will try it

Let me know if that works for you.

I just installed the version you linked to which is labeled at 2.7.1 and installed it and it seems to have fixed the problem. So, now I have an upgraded version and it works with Additional Categories.

Thanks, Sean

PS. I sure do wish that Additional Categories was a core feature of K2.

I 've let you down once. Won't do it again in this post :)

Thanks. I guess. :-)

Was this something that you had once planned to do but then decided against?

The reason I ask is that somehow I thought I had read that additional categories was going to be part of a later iteration of version 3?

But, maybe I was just dreaming. Stranger things have happened before.

I sure would like to know the best third party solution to add Additional Categories since I needed them.

Sean

We were always against it,
I prompted some users to request it on v3's repo, where once again we decided against it.

It is probable that you read that post and you misunderstood our intentions.