[CentOS] x86_64 server OOM problems after update to 5.3

Hello,

Over the weekend, I upgraded one of my servers that runs mysql and pdns
to 5.3. Previous to the update I have not had an issue form this server.
But since, I have had mysql die multiple times from oom-killer.

$ uname -a
Linux rack2a 2.6.18-128.1.6.el5 #1 SMP Wed Apr 1 09:10:25 EDT 2009
x86_64 x86_64 x86_64 GNU/Linux

Unfortunately, the server has been rebooted by others before I have been
able to look at it while the problem is occurring. But I have found this
in the logs:

http://pastebin.centos.org/25553

Running sar -A:

http://pastebin.centos.org/25556

Since the server was rebooted, the amount of swap is used is 0.

How do I determine what process is/was chewing up the memory on this
server? What should I be looking for to narrow this down?

Thanks,
Rick