When I post a comment , it opens a blank page with the following text:

{"message":"Comment added! Refreshing page...","refresh":1}

Same with all error messages.

Any ideas on what might be causing this and a quick fix ?

Solved the problem... jquery wasn't loading properly .

I have exactly the same problem. How do I fix it?

The jquery settings are in the K2 paramaters, at the top in the layout tab. Try changing them around a bit to see if it helps

Same problem - any solution?