prepareCall hangs

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

the jdbc code looks like      
        Connection con = poolingDataSource.getConnection();
        con.setAutoCommit(false);
        CallableStatement proc = con.prepareCall("{ ? = call \"insAccount\" ( ? ) }");

        proc.registerOutParameter(1, Types.OTHER);
        proc.setString(2,userName);
        this.registerCallableStatementForCancel(proc);
        logger.debug("registerCallableStatementForCancel(): exit"+userName);
/* another thread will call statement.cancel() if timeout exceeded*/
        proc.execute();
        this.unregisterCallableStatementForCancel(proc);
        logger.debug("unregisterCallableStatementForCancel(): exit"+userName);
        ResultSet rset = (ResultSet)proc.getObject(1);