Hey all, I've done quite a bit of searching and tried various things but nothing seems to be helping. I am trying to fix a Macbook Pro for a staff member here at work. It's a 2010 MBP running Lion. Twice now since upgrading to Lion he has experienced this issue. You see the login screen and enter your login credentials. If you enter them wrong you get the usual screen shake. If you enter them right, the screen flashes for a second as if it's going to login, then dumps you straight back to the login screen. I have tried Safe Boot, same thing. I have tried using Cmd+R, going into terminal and resetting his password, same thing. I have tried doing the same but for the root account and trying to login as root, again, same thing. It goes from working fine one day to totally unusable the next. Last time this occurred I had to restore his machine from a backup. SURELY there is a better fix then that? I would like to know what circumstances cause this issue as well so we can prevent it from occurring again. My 2011 MBP was upgraded to Lion the same day his was and I haven't had a single issue with it. Please, if anyone has any suggestions that I haven't already tried, I am all ears.