I reinstalled Mac OS X, Tiger. I went to software Update once everything was finished, to get everything up to date. After everything was done, it installed everything and then asked for system restart. I clicked restart. After it restarted it, it had the Apple logo screen with the little loading circle, after that there was a blue screen, then very slowly, the screen became darker starting from the top down, and very slowly. It then said I had to restart the computer. I've done this about 4 times, and nothing seems to happen. After it wouldn't work, I booted from a backup I made just before I reinstalled everything. What's going on? How do I fix this problem?