A Death, then a Downgrade

A few weeks ago I installed OS 7.5.3 on Aurora II, Apple has a free update to OS 7.5.5 so I tried installing it. When I finally got it on floppies it was a easy install, until afterwards, when I restarted the computer. The happy Mac came first, but then I got the black screen of death and the sad Mac. (Along with a few-keyed death hymn.) I was able to boot from floppies, but any system I copied to Aurora wouldn't boot it up. Without anything else to do I downloaded Mac OS 6.0.5 and installed it. To my amazement it worked, and so far is running great. So far the best part is that to shut down and restart take 12 seconds. Right now I'm downloading OS 6.0.8 and hopefully I came get it to dual boot 6.0.8 and 7.0.1 or 7.5.3.