Problems with temporary tables created in callable functions

Hi
I have a an application that uses a lot of stored functions, some of them which create temporary tables and refcursors that point to the tables. Something that comes up occasionally are errors like

This is when we have some code in the function to delete existing temporary tables.
ERROR: relation with OID xxxxx does not exist.
ERROR: relation "TEMPSTOCKVALUEALERT" already exists

When we comment that code we get errors like
ERROR: relation "TEMPSTOCKANALYSIS" already exists. This happens every second call to the function.

In the jdbc call code we have setAutoCommit to false, And I have tried a couple of options when preparing the call  like

        CallableStatement proc = con.prepareCall("{ ? = call \"queryStockAnalysisSingle\" ( ?,?,?,? ) }"
        ,ResultSet.CONCUR_READ_ONLY,ResultSet.CLOSE_CURSORS_AT_COMMIT);

        CallableStatement proc = con.prepareCall("{ ? = call \"queryStockAnalysisSingle\" ( ?,?,?,? ) }"
        ,ResultSet.CONCUR_READ_ONLY,ResultSet.HOLD_CURSORS_OVER_COMMIT);

None of them seem to work. Has anybody faced this problem? And hopefully cone up with a usable fix.
The application has a commons-dbcp maintaining a connection pool to the database server. The jdbc driver used is the jdbc3. THe database version is 7.4.x. It has been deployed on a Debian Linux system with kernel version 2.6.8.

Thanks
Akhil Srinivasan