killing a hung postgres process brings down the Postgres database server on MAC OS X!

Hi, there,

We are using PostgrSQL 7.3.4 on MAC OS X  G5  with Dual prpcessors and
8 GB RAM.

The postgreSQL server is our backend  that stores information for a
JBoss server.
Every once in a while, we see a process (thread) that processing a
request from
the JBoss server gets timed out.  Supposedly JBoss should clean up
after itself when it times out.
But it did not. If we do "kill -9 pid" to get rid of the deserted
process, it bring down the PG database
server entirely.

Is there a way to kill the dead processes/thread without really affect
the PG server?

Thanks!

Qing Zhao