PokerTracker

I have installed beta 16, and i cant use my existing database because the following message appears: "Unable to login to database (Pokerstars sits). Reason: server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request."

What can i do?

now i try to create a new database and the same problem appears.

That means that the postgres service isn't running.
Please try starting the postgres service: Start -> Programs -> PostgreSQL -> Start Service.
If that, and a reboot doesn't work, try stopping the service (Start -> Programs -> Postgres -> Stop Service), running a search on your computer for postmaster.pid and then deleting that file, then restarting the service and see if that helps.
Note that you may need to turn on 'View hidden files and folders', and the file seems to be in the folder './Program Files/postgresql/<version>/data'

i have tried it and it doesn`t work either. Maybe reinstalling postgreeSQL it will work? If so, my database would be erased?

Have a look at this post too: viewtopic.php?f=17&t=6332#p38285

Hopefully you won't need to re-install postgres but if you do, make sure you have a backup of your databases first. See the end of the Database / Postgres FAQ.
This FAQ explains how to uninstall postgres: Total uninstall/reinstall of pt3.

"You've both probably got a permissions problem that another piece of software has set on a file folder or a registry key that is stopping the postgres service get going.".

Reading this i have imagined that ie8 beta 2 maybe the reason for the problem. I installed internet explorer 8 beta 2 yesterday.
I have uninstalled it and the problem has disappeared.