JMS Topic shows increasing number of pending messages

[R Sin]

Application Server: WebLogic 6.1 sp2
Database: Oracle 8i
OS: UNIX (solaris)
Issue:
Messages (XML documents) are received at a JMS Queue and are then routed via a session bean to a JMS Topic. The Topic then sends them for processing to stateless session beans. Which finally insert/update to the database.
Noticed that while the "messages pending" at the JMS Queue is zero, the rate of "messages pending" at the Topic is steadily increasing. A vmstst on the server shows that idle time is 95% and from the WL Console, the idle thread count is around 9 (using default of 15).
BEA said that this was a known defect on WL 6.1 sp2 and we are using a patch from them, but doesn't seem to help. Database looks OK.
Thanks.