Cygwin-Postgres-IpcMemoryCreate - Function not implemented

I'm getting this error message when attempting to start postgresql:

$ postmaster -D /usr/share/postgresql/data/ &
[1] 2624

hurstm2(at)HURST-MARTI36 /
$ IpcMemoryCreate: shmget(key=5432001, size=1441792, 03600) failed:
Function not
implemented

I'm running under a Cygwin window, on a Windows XP operating systems, 256
MB ram, 1Ghz Intel processor, with over 4Gb free disk space on my local
drive.
I was able to run postgresql successfully for several weeks up to now, in
this environment.

I have been experimenting with large tables, and had added 4 million rows
to a particular table.
Postgresql was still working fine up to this point.
Then I added another 4 millions rows to that same table, and also ran the
"vacuum analyze" utility afterwards successfully.
This now made the table contain 8 million rows.
I shutdown the postgresql database, and exited the cygwin window.

The next day, I got the above error message.
Is this something to do with having large tables, I'm not sure.

Anybody with ideas to correct this error condition.

Thanks,
-Martin