Gparted requires root access but if it is not setup to use root access it will just give an error and close.
To Get the functionality that most distributions have for such programs in KDE 4 just right click your porteus menu icon and select "Edit Applications", Find the application in question, for gparted this is under system. Go to the advanced tab and Check Run as different user and input root into the field, Now when the application is run it asks for the root password instead of bailing out.