fooloof 0 Newbie Poster

I've got an older Powerbook (PPC, not Intel) that has Tiger 10.4.11. Out of nowhere, it stopped logging in. When I start the computer, it starts up normally (the Apple logo and turning gear) but then goes to a blank blue screen. I've tried the safe boot and it appears to work but only up to a certain point. It gets as far as "logging in", but never completes the login (meaning my disk or other images don't come up). Interestingly, at this point, the screen is still blue, but has the swirling pattern that is my normal desktop background. I can move the cursor, too; but that's all. I've also tried "single-user mode" and it says that "10.4.11 appears to be okay." Please help! Many thanks.