Mac OS X 10.7.5 stuck in a "loop"
Please HELP!
Since yesterday I can't log in to the administrator, I didn't downloaded anything from the internet or installed a new program. I enter the password of the Admin (it's correct!) then the screen goes light grey, and a few seconds later back to the login page, and this happens in a loop!. I can get into the guest user but not where all my files are. I read all the discussions of the forum about this topic but please, I don't know where to begin. I've made a software update of Lion today but still in the loop.
Can please anybody help me? Thanks a lot.
MacBook Pro, Mac OS X (10.7.5)