md5 authentication issues with psqlODBC driver for Windows

I've been running into an issue where I get an error "password authentication failed" while using the psql ODBC driver for Windows, with the database residing on a Linux machine.

I know my current setup is (relatively) correct since:
1) I've previously used a JDBC driver with postgres and md5 authentication, with no problems (with Linux on both client and server)
2) In Windows I can look at the ODBC sources and always verify that I can connect to the database
3) I'm able to fix the problem by using trust instead of md5 authentication

Basically, I'm using the driver to connect the statistics program SPSS to a database. I can always connect to the database and see the tables, but the problem occurs when I try to make a query. The first time might work and actually return results, but after that, I consistently get the "password authentication failed" error.

Is there a chance this is a bug/human error with how I'm using the driver, or should I be on the SPSS message forum instead?

Thanks,

Chris