If everything else fails, you could reset all your user configuration files and reboot the system. BEFORE DOING THIS, check if the problem exists with a newly created user, so create a user, get back to gdm login screen, select the new user and test if the problem persists.
If everything else fails, unaweza kuweka upya mtumiaji yako files Configuration wote na reboot mfumo. Kabla ya kufanya, kuangalia kama tatizo lipo na user nybildat, hivyo kujenga mtumiaji, kupata nyuma gdm screen login, kuchagua mtumiaji mpya na mtihani kama tatizo likiendelea.