Finally solved a nagging problem in my wordpress test system. I was unable to edit some test users, not all – some were okay .
Message received was:
Catchable fatal error: Object of class __PHP_Incomplete_Class could not be converted to string in C:\web\wp28\wp\wp-includes\formatting.php on line 405
I had previously worked through another problem with this 9640 patch. While it fixed another problem, I then started to get this one. Eventually I found this http://lists.automattic.com/pipermail/wp-trac/2009-July/053190.html, and it dawned on me,
A test system – plugins not fully uninstalled….Hmm… In testing amr-users, my user reporting plugin, I have had several plugins installed that create user data, not all of them active now. I dived into phpmyadmin, deleted any usermeta that related to plugins not in use, and viola – user editing problems fell away