As discussed in various places - devel list, https://bugs.archlinux.org/task/24615 , and http://sourceware.org/bugzilla/show_bug.cgi?id=13013 - current glibc contains a bug which can cause any app to crash if a DNS lookup fails in a particular way (so far as I can tell). Usually the bug is hard to reliably reproduce - just trying to browse to a garbage domain doesn't do it - but https://bugs.archlinux.org/task/24615#comment78282 claims this as a reliable reproducer:
# iptables -A OUTPUT -p udp --dport 53 -j REJECT --reject-with icmp-admin-prohibited
# wget http://google.com/
--2011-06-08 12:13:58-- http://google.com/
Resolving google.com... zsh: segmentation fault (core dumped)
http://sourceware.org/bugzilla/show_bug.cgi?id=13013 has a proposed patch, which I will attach to this report. Kevin Fenzi did a scratch build - http://koji.fedoraproject.org/koji/taskinfo?taskID=3289243 - with the patch, which he says seems to resolve the issue for him. That report also suggests that the condition to cause the crash is "When the first answer is a SERVFAIL, NOTIMP or REFUSED".
Created attachment 519536 [details]
Proposed fix (from Aurelien Jarno, Debian)
proposing as Beta NTH and final release blocker, this is a bit icky of a bug to ship with.
holy cow, it's groundhog day. I already reported this one and promptly forgot. sigh.
*** This bug has been marked as a duplicate of bug 730856 ***