problems with 6.3 and JDBC

Hello,
I changed from postgres 6.2.1 to 6.3.2 and now i get following error
message:

Exception trying to connect database: java.sql.SQLException:
Connection failed: java.net.ConnectException: Connection refused
java.lang.NullPointerException

I used the 6.2.1 postgresql.jar, cause there wasn`t any in the 6.3

Does anyone know the problem?

Thanx Bernhard