problem about postgresql and jdbc

Hi,

i have trouble using PostgreSQL7.1.3 via jdbc on my Windows XP System
(using the actual cygwin distribution and j2sdk1.4.0).

The Database sends following error message after connection:
PacketReceiveFragment: read() failed: Connection reset by peer

The Java Program prints following stack trace:
---Single simple object test and transaction test
pl.PlException: org.postgresql.util.PSQLException:
Something unusual has occured to cause the driver to fail.
Please report this exception: Exception: java.lang.NullPointerException
Stack Trace:
java.lang.NullPointerException
at org.postgresql.Connection.openConnection(Unknown Source)
at org.postgresql.Driver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:512)
at java.sql.DriverManager.getConnection(DriverManager.java:171)
at pl.test.PostgresqlDatabase.getNewConnection(Unknown Source)
at pl.sql.RelationalDatabase.getConnection(RelationalDatabase.java:278)
at pl.PersistenceManager.getConnection(PersistenceManager.java:927)
at pl.PersistenceManager.saveObject(PersistenceManager.java:289)
at pl.PersistentObject.save(PersistentObject.java:133)
at pl.test.Test.performTest(Unknown Source)
at pl.test.Test.main(Unknown Source)
End of Stack Trace

Thanks in advance,
Yousry