Could my issue be the same problem as this thread?:
http://archives.postgresql.org/pgsql-bugs/2005-11/msg00114.php
The references to "Invalid Argument" caught my eye. That thread
did start from a very different point, though.
-Kevin
It's possible. You said that the log file wasn't working, and you can reproduce the error, so the first thing I would do is solve the logging problem, then reproduce the error and see what the log says.
I'm not familiar with pgsql on windows, but check to make sure you have logging turned on in the postgresql.conf file (this is on by default). Make sure you are logging to a file and directory that the pgsql service has permissions to write to.
Does the windows system log give you any errors or warnings when pgsql starts? Perhaps it will describe why it's not logging.
-Josh