Sometimes (don't see any rules why this happen and I'm not able to reproduce it, it occurs randomly) when new user is created and one would like to edit him, the dialog window appears with admin user name instead of his regular name (the link of the dialog is different that it's with correct behavior). This has the impact on storing the updated user account - it's not possible and the error (log is attached) appears. Once the dialog is closed and the user is edited once again, there is no problem like that.