Attempting to erase the NAND flash via the ATK tool did not succeed, but it cleared the problem, mostly. THere are warnings about 'stale lock file' and the file system has issues now, but it's running again.
Now, the issue is: why do I get erase failures? I tried to reflash RedBoot according to the IMX27 PDK Linux Demo Readme, and it fails, too.
Anyone have any idea which way I should go next?