postmaster won't start under cygwin after password change

I asked on cygwin but no answer yet; maybe someone here knows.

I've been running PostgreSQL 7.4.1 successfully for a few weeks under an
updated cygwin, but it stopped working over the weekend.  That happened
to be the time XP Pro decided my postgres password should expire.  I
gave it a new password, as requested, but postmaster still won't start.
ipc-daemon2.exe is running.

When I tried to start the postmaster as postgres and not as a service
using

postmaster -D /var/postgresql/data

I got

LOG: shmdt(0xf90000) failed: invalid argument
LOG: database system was shut down at 2004-03-21 09:04:56 PST
LOG: checkpoint record is at 0/1DB0E00
LOG: redo record is at 0/1DB0E00; undo record is at 0/0; shutdown TRUE
LOG: next transaction ID: 3987; next OID: 18937
LOG: database system is ready

but when I try cygrunsrv -S postmaster

I get a Windows error 5 (logon).

Suggestions?  I do have a backup of the database, so I guess I could
start over.  I guess I'm trying to figure out where to start in
/cygwin/usr/share/doc/Cygwin/postgresql-7.4.1.README.

Thanks,

Bill