When I turned my iMac on this morning (iMac G5 PPC 10.5.8) it went through all of the "normal" steps (gong, grey screen, apple logo, progress wheel, blue screen) and stopped at the blue screen. Thinking it was just a fluke, I shut the machine down and restarted, only to have it stop at the blue screen again. After disconnecting everything going into the iMac except the keyboard and mouse, I attempted to boot into safe mode but it stopped at the blue screen again. I tried single user mode too but I didn't get any further than the blue screen. Next, I flashed the PRAM (big gong, single quieter gong) and afterwards it came to the blue screen. I reattached my external drive and selected to boot from a 2-day old backup. Using the backup I was able to log into both my regular account and my "test" account (without login items). I still cannot login (except to my external drive backup). Any ideas?