@ Gúrú Linux ríomhaire
I am not getting exactly what you are describing, so I still don't understand.
The login screen, a white screen with an environment dropdown box at the lower left, has the following choices. Each requires that I enter my password to continue.
Default [this choice gives me an error "unable to launch 'startlxde" X session... falling back to default session" and clicking on "ok" gets me a blank screen where the mouse shows but right clicking gets nothing and I have to do a hard shutdown]
Lubuntu Netbook [this choice gives me a simplified version of the Lubuntu environment. I am attaching a screenshot. Obviously it's not Gnome.]
Lubuntu [This is the environment I am using but which I want to switch to the Gnome you are using. See screenshot]
Gnome/Openbox [this just loops me through User/PW entry > User/PW entry > etc. It never gets out of this white page and doesn't put me into the Gnome environment. There is no error message.]
KDE/Openbox [choosing this does same as Gnome/Openbox.]
Openbox Session [this choice gives me a blank screen and cursor arrow after login and password, but right clicking the cursor arrow gives me menus with all the program choices that Lubuntu and Lubuntu Netbook give me. But it's not Gnome, obviously. No icons, no top or bottom bars, just menus with a right click of the mouse.]