Anybody know of a good rescue CD/"live" Linux boot CD for Macs? Something like Knoppix for the PC architecture. I'd like to use it to rescue my PowerBook.
It sounds like you have bigger problems than needing a command line to copy files.
You can't boot from your hard drive. You can boot from a CD. You can access the hard drive if you boot from a CD. You can reinstall the OS from the CD, but can't boot to the newly installed OS. You reset the PRAM and NVRAM. Have I correctly summarized your situation?
How much RAM do you have? What kind?
This is the oddest thing I've heard of for a while. When a lowly security update makes a computer stop booting and neither resetting NVRAM/PRAM nor a new OS fixes it. It doesn't add up.