The setup:

2x Replica Pairs
1x Config Server
1x Mongos server

Script running inserting data into database test.

1. From mongos machine, drop database that script is inserting into
2. Shut down config server. Leave everything else running. Wipe out data/db dir.
3. Restart config server
4. Mongos crashes with the following error:

Tue Nov 17 23:07:54 ./mongos v0.2.5 (alpha 2.5) starting (--help for usage)
Tue Nov 17 23:07:54 git version: aa8b12e13fbbdfb293d94786dcc0df589cabef99
Tue Nov 17 23:07:54 sys info: Linux ofc-n1.10gen.com 2.6.23.17-88.fc7 #1 SMP Thu May 15 00:02:29 EDT 2008 x86_64
Tue Nov 17 23:07:54 waiting for connections on port 27017
Tue Nov 17 23:07:58 connection accepted from 192.168.8.32:33937 #1
Tue Nov 17 23:07:58 couldn't find database [test] in config db
Tue Nov 17 23:07:58 can't find a server
Segmentation fault