Every table is declared as either a PG or Oracle table, right? No changing prop:owner on a table.
What is your prop:BusyHandling setting?
Do you use /TurboSQL on any table in the system. I had to abandon TurboSQL in systems that connected to multiple databases because the system would attempt to use the wrong database. Not just with the TurboSQL tables, but regular tables, too. Using TURBOSQL driver string for a normal SQL table?