I have long been using F16 on my machine (Asus K52F). I recently installed F17 on another partition (overwrote Windows at last!). F17 works fine. But now I can't log in with F16 (which for a short transition period I need to do). All well to the login screen; then when I enter the correct password, the screen goes black for a few seconds, then returns to the login screen again. (If I enter an incorrect password it tells me that the password is incorrect; so it is not that the password has somehow changed.) I tried Ctrl-Alt-F2, the terminal with 'log in:' - it gives 'password incorrect' if I use a wrong word, but simply returns to 'log in:' if I do give the right password. Thanks for any help to get F16 up again for a while, even if nec. as root.