I forgot to add that in investigating this problem, I zapped the PRAM numerous times, including once in which I followed the Apple instructions of letting it bong 3 times before releasing the keys. I also replaced the PRAM battery (which needed replacing anyway). I didn't think the battery was the problem as I could reboot with no battery installed and get the exact same results, but since I had dissected the machine it simply made sense to replace it. There are only a few sites on the web that sell the 4.5V battery needed by the LC 575, but Radio Shack sells single battery holders for N-cell batteries so it was pretty simple to create my own battery with 3 N cells connected in series. It ends up being almost the same size and can be attached to the same velcro patch on the motherboard. That said, I'm not recommending it to anyone except the most impatient (such as myself) since it ends up costing almost the same (N cell batteries are pricey at Readio Shack). Of course, if I still have this machine in 10 years I won't have any problems finding replacement batteries...