libpq won't connect when client is built with MinGW

Hello, I've been trying to get a simple test program built on Windows XP
Pro SP2 using MinGW 4.1.0 + MSYS 1.0.10. I am using the standard
"postgresql-8.0.4.zip" download with the development libs selected
during install.

Everything builds nicely, but whenever I try to do a PQconnectdb with an
IP address (hostaddr=10.0.0.23), I get the following from PQerrorMessage:
--
could not create socket: The requested service provider could not be
loaded or initialized.

(0x0000277A/10106)
--

And when I try it with a host name (host=testdb), I get the following
from PQerrorMessage:
--
could not translate host name "testdb2" to address: Unknown host
--

BTW, the computer can resolve testdb2 to 10.0.0.23 just fine... Any ideas?
Here is the output of my build script (as created by Eclipse 3.1 + CDT 3.0):

--
**** Full rebuild of configuration Debug for project HelloWorld ****

make -k clean all
rm -rf ./main.o ./main.d HelloWorld.exe

Building file: ../main.cpp
Invoking: GCC C++ Compiler
g++ -IC:\Program Files\PostgreSQL\8.0\include -O0 -g3 -Wall -c
-fmessage-length=0 -omain.o ../main.cpp
Finished building: ../main.cpp

Building target: HelloWorld.exe
Invoking: GCC C++ Linker
g++ -LC:\Program Files\PostgreSQL\8.0\lib -oHelloWorld.exe ./main.o -lpq
Finished building target: HelloWorld.exe

Build complete for project HelloWorld

--

Stefan T. Peters