Thanks for all the advice. I had some mismatched libraries,
and cleaning up that was probably a good idea.
Still, the problem persisted.
It turns out that "cvs up" always complains if local changes
are in the way. "svn up" never complained, so I thought
everything was ok. But it turns out that "svn up" never complains,
and now I feel silly.
"svn revert -R *" purged the remains of some old performance
patches I tested - and then my 64-bit lyx ran just fine.
So be warned, "svn status" or "svn diff" is needed to notice
wrong files.
Helge Hafting