Unexpected VACUUM FULL failure

This is a bit disturbing:

*** ./expected/vacuum.out    Sat Jul 20 00:58:14 2002
--- ./results/vacuum.out    Wed Aug  8 20:16:45 2007
***************
*** 50,55 ****
--- 50,56 ----  DELETE FROM vactst WHERE i != 0; VACUUM FULL vactst;
+ ERROR:  HEAP_MOVED_OFF was expected DELETE FROM vactst; SELECT * FROM vactst;  i 

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This is today's CVS HEAD, plus some startup/shutdown logic changes in
postmaster.c that hardly seem like they could be related.

I couldn't reproduce it in a few tries.  A reasonable guess is that
it's triggered by autovacuum deciding to vacuum the table sometime
before the VACUUM FULL starts.  Anyone want to try to reproduce it?
        regards, tom lane