Consever crash and teminated with "out of memory" in conserver log

Dear conserver users,

I'm using CentOS release 5 (Final) with 4G physical memory. I have been
using Consever for two years. Recenty, Conserver crashed frequency with
message at
/var/log/conserver as
conserver: out of memory
[Thu Feb 10 15:53:08 2011] conserver (31728): child pid 31736: exit(69),
shutting down
[Thu Feb 10 15:53:08 2011] conserver (31728): terminated

I checked the usage of memory and found it's still more than required
still no in use.
Anything I can overcome or work around the problem?

Thanks a lot
Alfred Chau
ITSC
HKUST