So I think the problem arose because I had a copy of OpenSSH installed, which includes cygwin (apparently). So, there was already a copy of the cygwin dll on my system.
Note that the CygWin setup MADE NO ATTEMPT TO DETECT THIS!!! The only way I found out what was up was to install the PostgreSQL 'proof of concept' native Windows install PgSQL731wina1.exe then when I ran the PostgreSQL command shell, I was given a message about two copies of the DLL on the system. If CygWin setup tried a LoadLibrary or similar on the main DLL before proceeding with the install, you'd easily be able to prevent this...! cheers, Tom Gilbert [not the linuxbrit guy, by the way]
