SQL & PL/SQL

hi gurus,

we have a java written application that calls some stored procedures (9i). those procedures are using different tables.
everything worked fine for a long time but today we've noticed a strange behavior:
when one stored procedure is triggered, other procedures executed while the first one is still running are blocked and wait, until that first procedure is ending. this happens with all procedures, their execution is not concurrent anymore.
the java's callablestatement.execute() method is called, but the logs in pl/sql show that a stored procedure function is not triggered, this until any other stored procedure is running. no exceptions are thrown, all procedures are executed in a queue.
we think our dba could change something, but he is out of office and totally not available now... any ideas are welcomed!
thank you for your time.