Benutzer und Gruppen

repair permissions with disk utitliy, reboot and try again.

If all fails you might want to consider a clean install ( no update/upgrade ) . Creating a bootable USB drive or DVD is easy : Inside the "Install OS X Mountain Lion " app is included a dvd image file ( containing the letters .."ESD".. ) , simply restore this to a disk or thumbdrive and boot the mac from it.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the page that opens.

Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left.

Click the Clear Display icon in the toolbar. Try the action again. Post any messages that appear in the Console window – the text, please, not a screenshot.

Important: Some private information, such as your name, may appear in the log. Edit it out by search-and-replace in a text editor before posting.

Launch the Terminal application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Terminal in the page that opens.

Drag or copy — do not type — the following line into the Terminal window, then press return:

dscl . -list /Users | grep Guest

Post the lines of output that appear below what you entered, if any — the text, please, not a screenshot.

It looks like you have a corrupt user picture.

Back up all data if you haven’t already done so. Before proceeding, you must be sure you can restore your system to the state it’s in now.

Launch the application

/System/Library/CoreServices/Directory Utility.app

which you can do by selecting the above line in your browser, right-clicking (or control-clicking), and selecting Services ▹ Open from the contextual menu.

In the application window, click the lock icon and authenticate. Select the Directory Editor tool in the toolbar. Select Users from the Viewing menu in the toolbar, if not already selected. Select your user account in the list. On the right is a list of properties and values. Select the property "JPEGPhoto" and delete it by clicking the minus-sign icon below. Then click the Save button in the lower right corner of the window. Quit Directory Utility.

Try again to open Users & Groups. If it still doesn't work, repeat the above steps with any other users you created. Don't change any built-in user accounts.

Upgrading from SL directly to ML, had the same issue, and your solution worked!!

Thank you very much.

Giorgio

great, thanks a lot