Serious connection problem

I just installed (for the 4th time) Postgresql 8.01 on WinXP SP1. Each
time, the same thing happens. When I use pgAdminIII to connect to the
default database server, I get the following error:

"An error has occured:
server closed the connection unexpectedly
This probably means the server terminated abnormally before or while
processing the request."

I have set up a user account (ie: not admin account) in WinXP for this
installation. I have also set listen_addresses = '*' in
postgresql.conf. The install procedure seemed to run without flaw. I
have even uninstalled Norton Antivirus. The machine has a Network
Bridge on it because it is used to bridge the wireless connection that
is hardwired to the machine. I mention this just in case it has
anything to do with this problem. This machine is obviously not going
to be a production server, but for development only.

When the postgresql service starts, the log file is filled with the
following statements repeatedly:

FATAL: could not reattach to shared memory (key=5432001,
addr=01350000): Invalid argument
FATAL: could not reattach to shared memory (key=5432001,
addr=01350000): Invalid argument
2005-02-11 15:06:52 LOG: background writer process (PID 2016) exited
with exit code 0
2005-02-11 15:06:52 LOG: terminating any other active server processes
2005-02-11 15:06:53 LOG: all server processes terminated; reinitializing

How do I fix this connection problem?