what units are "18.0" and "20.0"?
check the size with
ps aux and take the value from VSZ.
The "memory leak" is rather "memory fragmentation", which is one of the reasons why busy sites should consider a daily restart.
have you checked the used libraries with ldd? What is your host operating system?
have you checked in the core dump file, where the crash happens? use gdb, see e.g. http://www.ibm.com/developerworks/library/l-gdb/.
It is true that you postgres configuration should be tuned, but that won't crash the aolserver. The error is a segmentation violation, which means that the process tries to access memory not part of its accessible memory. In most cases, this is due to an erratic pointer in a C-Program, but in general, the error can be triggered by multiple causes. Check the following thread and FAQ:
http://lists.debian.org/debian-user/1997/04/msg01588.html
http://www.bitwizard.nl/sig11/
If you are really confident that onbody has changed shared libraries etc. then it might be the hardware. If you have the option, move the installation to a different hardware and test it there. It is certainly worth to run extensive hardware checks.
-gustaf neumann
