I upgraded 1.86 version to 1.87 version without any problems.
Now it seems there have been some changes in file locations? on ajax?
The file: groups/index.php has a require_once line which wont work because of the require_once('HTML/AJAX/JSON.php');
I thought Moodle wasnt dependent on pear-modules? because that require_once line tries to find the ajax-module in my pear-directory. Correct me if Im wrong.
My fix was to install pear module HTML_AJAX!
After this I got the groups page working again, but when I try to see the attendants on different groups it wont show them on right side. I have to go "Add/remove users" to get the list.