My PB 180c that I got recently has a strange software issue.

I get a Happy Mac on startup, then a blank grey screen, and then a floppy icon, which means that something inside the System Folder is borked in some way. I've booted from a Disk Tools disk, repaired the HD with Disk First Aid (which is fully working and still has installed software and OS 7.1, with the appropriate enabler), and the same symptom exists still. Any ideas?

Nothing really seems to be missing from the System Folder.