PokerTracker

What is the recommended Postgres version for a 64bit PC?

The latest 9.0 version, which is currently 9.0.8.

Anywhere some steps on upgrading?

It depends on your current setup - if you already have a lower version of 9.0.x you can just run the latest 9.0.x installer.

If you have an older version of PostgreSQL (8.3 or 8.4) and want to convert your existing databases you will need to make a backup using the old service (via the menu File > Backup). Then you can install the new version (9.0) - I'd suggest specifying a different port when you install 9.0 (maybe 5490 instead of 5432) so that you can use either service just by changing the port you use when creating a database.

Once you've installed 9.0 run PT4 and create a new database specifying the new port number to connect to the 9.0 service, then use File > Restore to restore your existing database to the new service.

What's the specific issue with 9.1 again? I've seen reports on crashes and data corruption with PokerTracker, but is this because of errors in PostgreSQL or because of something PT does which breaks compatibility? Just curious.

The problem is in PostgreSQL 9.1, although I don't know the technical details personally.

Our tests have shown these are errors in PostgreSQL - bad data ends up in the database in addition to various crashing issues. Since we just use COPY and UPDATE to get data in and change them it isn't really anything special we're doing.

I have 9.1 installed. Do I have to uninstall psql and start a new database from scratch or is there a simple way to downgrade it?

Backup your database using PokerTracker's Backup mechanism (File -> Backup). Then uninstall 9.1 and install 9.0 and restore via File -> Restore in PokerTracker. That should be all you need to do (though once everything is working properly you probably want to delete the 9.1 data directory manually as it could be large depending on your database size).