SQL Exception Relation xxx does not exist

Hi,
I am getting the following error when running an update from a JAVA
program using a Tomcat Connection Pool.

SQLException: Error Relation 215106760 does not exist

In the server log I see additional info Error occured while executing
PL/pgSQL function funcName
line 105 at select into variables

I dont think that the Function has a problem as I am able to run it with
the same parameters from within psql returning me a result.

The strange thing is that it works for a couple of day. Once I restart
tomcat the problem goes away... for a few days. Although I use many
objects from the same Servlet, only this particular PL/pgSQL function
has a problem.

Question:
1. Is that problem known in PG7.3.4?
2. Could this be a problem with the connection pool of tomcat or the
postgres JDBC driver ?
3. how do i find out the name of the actual object referred by 215106760
in the error message?

Thanks for any help

Alex