Try running the commands in a terminal, and see what messages are shown. Normally since they are admin type apps, you should get a popup (which is esu off the Admin menu) to enter the root password. Try that approach, too: run esu, then enter the synaptic or gparted command after putting in the root password. Yet a third would be to enter
su -c synaptic at the command line in a terminal. These are workarounds, but you can post the error messages here. Have you also checked out the latest dev version?