Update on this issue. I think it might have something to do with the following bug in Red Hat bugzilla: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=91933
It appears to have something to do with some combination of NTPL and errata versions of the kernel, db4 and glibc packages. I've rebooted into the older kernel (2.4.21-20), but that didn't help. I'm using the original db4 (4-4.1.25) from WBEL, and I'm rebuilding glibc-2.3.2-95.20 from source rpm. I'm dreading the thought of forcing an older glibc into place, but I'm hopeful that might fix it.
Updates to follow (assuming my server survives the process)...
-- Jason Dixon DixonGroup Consulting http://www.dixongroup.net