[CentOS] CentOS 5.2 - /usr/sbin/httpd: double free or corruption (!prev) error

Hi List,

We've been seeing the following error on a CentOS 5.2 x86_64 /  
2.6.18-92.1.6.el5 install (from /var/log/httpd/error):

	*** glibc detected *** /usr/sbin/httpd: double free or corruption (! 
prev): 0x00002ad8ebed2d80 ***
	[Thu Jul 10 19:12:19 2008] [notice] child pid 5261 exit signal  
Segmentation fault (11)
	[Thu Jul 10 19:12:48 2008] [notice] child pid 12180 exit signal  
Segmentation fault (11)
	...


The following packages are installed:
	glibc-2.5-24
	httpd-2.2.3-11.el5_1.centos.3
	mysql-server-5.0.45-7.el5
	mysql-5.0.45-7.el5
	php-gd-5.1.6-20.el5
	php-mysql-5.1.6-20.el5
	php-common-5.1.6-20.el5
	php-pdo-5.1.6-20.el5
	php-cli-5.1.6-20.el5
	php-5.1.6-20.el5
	php-imap-5.1.6-20.el5


If we remove the php-pdo / php-mysql packages, then the crashes stop.  
But, we need those packages, so that's not a solution.

Any ideas as to what might be causing this?

We've tried the obvious things; the only thing that's not "vanilla"  
here are a few settings in /etc/php.ini (having to do with max  
execution time and max memory). The php code that's being run does  
have its share of php warn/notices:

	PHP Notice: Undefined index: d in [snip] on line 1699
	PHP Notice: Undefined index: verbose in [snip] on line 1819
	PHP Warning: Invalid argument supplied for foreach() in [snip] on  
line 1695

So I would not be surprised if it is tickling something out of the  
ordinary, but it should still not be causing a segfault!

Any thoughts as to what's going on here, and how to fix it? I'm  
tempted to install php 5.2.6 from utterramblings repo, to see if that  
works around this.

Thanks!