Following a tip in this forum, I recently installed xfce4 in LMDE (using Synaptic) so I would be able to choose between xfce and gnome in the login window. This worked perfectly, until I decided to change the screen resolution in xfce and accidentally picked one that is too high for my monitor. Now everytime I open an xfce session, the screen goes black after the login screen and my monitor displays an error about the resolution being too high. I can however still login by pressing CTRL-ALT-F1, but there is no way I can get into the graphical environment. I have looked around on the internet for a solution, but haven't found one. I tried the xrandr command, but that only gives me a "cannot open display" error. I also tried re-installing the nvidia drivers using sgfxi, thinking that would solve it. The installation was succesful, but unfortunately it didn't fix the black screen.
So I switched back to gnome and forgot about xfce for a while, until yesterday I managed to break something in gnome that gives me the exact same problem as in xfce. This time however I didn't even change the resolution, but the problem appeared after uninstalling and reinstalling Evolution Mail. At least I think that's what caused it, I'm not sure. Perhaps I accidentally uninstalled an important component for gnome when I was uninstalling Evolution, I don't remember exactly.
Anyway, I now don't have any graphical environment anymore in LMDE. Not xfce, and not gnome. Is there any way to fix this or will I have to restore my whole partition?