Some more information has cropped up. Instead of a reset-inducing crash on save, I actually got an error message that could be helpful:
http://img341.imageshack.us/img341/9193/hderror.jpg HD0 has a blockid error in block 4104. Expected was blockid 0x4F424A43, but the block says it is blockid 0xFDFDFDFD. Also my 430 meg HD no longer boots, so it's no-going back now... A search for this type of error message suggests I run SFS Doctor, but that program seems to be just for MorphOS. This is a WB3.1 install.