http://bugs.winehq.org/show_bug.cgi?id=30452
--- Comment #8 from Peter L Jones winebugs@drealm.info 2012-04-16 09:29:30 CDT --- The delete of ~/.wine does appear to be what fixed it - the dll that now resides in ~/.wine/drive_c/windows/system32/usp10.dll is identical to /usr/lib32/wine/fakedlls/usp10.dll from wine-1.5.2 dated 12 April 2012.
I can only agree with your conclusion that somehow my ~/.wine copy of the dll was damaged. I don't have a back-up of my home directory to hand to check, unfortunately.