installed mountain lion now computer will not allow me to enter just says restart

It took 24 hours to finally download os x mountain lion on to lion and now after it says 'install' and restart, the computer will not allow me to enter. The grey Apple screen comes on with some DOS lettering(or whatever that is that says 'panic'. . ..and about 10 other line. screening over the grey secreen. Then a black square with white lettering comes up in the center of the grey apple screen and says to restart. WE repeat the cycle with every start. However I was able to get into a solid grey screen on the 'guest account' where I have no access to any of my files, but I can get to the previously viewed websites!!!