z50 POST error 203?

I've got a z50.  Last night, I started compiling a new kernel.  Left it
on, building, overnight.  When I got up and looked at it, it was done
(apparently normally - it failed, because I had forgotten my kernel
source tree was not in buildable shape).  So I unplugged the ethernet
and mains power brick, moved it into another room, and tried to start
working with it.  No response.  I couldn't get any response at all.

So I removed the battery and put it back, which is my usual recovery
procedure for total wedging.

But now it won't POST.  I get the startup screen with the IBM logo in
the upper right, the WorkPad name in the lower left, the text

ROM Version S3A61 Feb 9, 1999
VR4121 at 131.1 MHz.

in the extreme upper left, and a line of dots at the extreme lower
left.  Usually, the dots appear one by one until some five or ten have
shown up, then it drops into WinCE.  This time, it prints three dots
and then "203".  It hangs there, the orange "disk activity" light
flashing at about 1.3 Hz, for as long as I've been willing to wait
(several minutes, at least).

I'm going to be looking for maintenance docs, of course.  But I'll be
surprised to find anything more helpful than "replace FRU #xxx" in any
docs I find; if anyone has anything more useful to suggest, or
experience with such POST errors, I'd love to hear.

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