Hmm...It seems I was barking up completely the wrong tree. Everything now
works as I would expect without having to use a transaction.
I'm not exactly sure why but I think it may have been permissions...I
dropped the database and recreated it so it was owned by the user trying
to do the update and now it works fine.
Questions that now come to mind:
1) If it was permissions why did the returned result from PQExec indicate
everything was OK?
2) If it was permissions how come nothing is logged in errlog?
3) If it wasn't permissions what was it?
4) Is there any way to chown a database and tables? I'm guessing its an
update on some system table?
Thanks to Brett McCoy for his assistance,
Andrew