If I stop GDM and call xinit as an ordinary user, everything works as expected, e.g. I can start Lyx from the X Term window, and no letters are missing &c.
If I start gnome-session from the same X Term window as a user who has experienced the problem under GDM, the problem appears just as it does under GDM. For a new user, the session started is of the “classic” variety (not the new Gnome one) and works perfectly! At the beginning, an error message appears about hardware problems making it impossible to run the new Gnome session type. Unfortunately the message disappears too quickly. Switching back to GDM: whereas the new Gnome session type does not work at all (as described), so-called classic sessions work nearly perfectly. Sometimes small parts of the screen remain blank but are drawn correctly if a cursor is moved there.
