FastPath call returned Error: Relation doesn't exist

Hello everybody.

I am facing a rather strange problem and hopefully someone here can help me 
out. (urgent, do I need to mention ? :) )

I am using Tomcat 3.1.1, JDK 1.2.2 and postgresql 6.5.3-6 (from RPM) on 
RedHat 6.2.

I got a Fastpath Protocol Error: Z  all the time last week, when trying to 
access
the dbase using the jdbc6.5-1.2.jar driver.
After having searched the net for a reasonable answer, I didn't find one 
and went for PostGreSQL 7.0.3 (aswell form RPM)
and after changing the servlet properly (who got the idea to add an org. to 
the access path anyways?) , I got this error:

FastPath call returned ERROR:  Relation 19750 does not exist

(plus my stacktrace)

This error comes up with the jdbc7.0-1.2.jar driver.
The curious thing actually is, that the dbase was accessed a few times 
before that error comes up.
After the error has occured, the dbase is not accessible anymore through 
the servlet.

postgres is set up fine it appears, since phpPgAdmin, psql and other 
commandline tools just work perfectly.

This is really driving me nuts, since it is supposed to work out fine. Also 
the FastPath protocol error mentioned
above I am not able to resolve. I take any solution really.

I read somewhere there may be a fixed version of the JDBC6.5-1.2.jar which 
deals with the protocol error,
but the link to the postgres pages with a /jars/ directory was gone ...


PLEASE ... someone help me out ...

---
Andreas Rust, webnova GmbH