see below. without --fork and --logfile i got different, slightly prettier error message.

Wed Oct 13 12:29:29 mongo/bin/mongos db version v1.7.1, pdfile version 4.5 starting (--help for usage)
Wed Oct 13 12:29:29 git version: cee2d0d6816a704126c283401db24c949d5f52a3
Wed Oct 13 12:29:29 sys info: Linux domU-12-31-39-06-79-A1 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_41
Wed Oct 13 12:29:29 warning: couldn't check on config server:mongo01:27019 ok for now
Wed Oct 13 12:29:29 SyncClusterConnection connecting to [mongo01:27019]
Wed Oct 13 12:29:29 SyncClusterConnection connect fail to: mongo01:27019 errmsg: couldn't connect to server mongo01:27019
Wed Oct 13 12:29:29 SyncClusterConnection connecting to [mongo02:27019]
Wed Oct 13 12:29:29 SyncClusterConnection connecting to [mongo03:27019]
Wed Oct 13 12:29:29 trying reconnect to mongo01:27019
Wed Oct 13 12:29:29 reconnect mongo01:27019 failed couldn't connect to server mongo01:27019
Wed Oct 13 12:29:29 MessagingPort say send() errno:9 Bad file descriptor 172.30.200.3:27019
Wed Oct 13 12:29:29 query failed to: mongo01:27019 exception
Wed Oct 13 12:29:29 MessagingPort say send() errno:9 Bad file descriptor 172.30.200.3:27019
Wed Oct 13 12:29:29 query failed to: mongo01:27019 exception
Wed Oct 13 12:29:30 MessagingPort say send() errno:9 Bad file descriptor 172.30.200.3:27019
Wed Oct 13 12:29:30 query failed to: mongo01:27019 exception
Wed Oct 13 12:29:30 MessagingPort say send() errno:9 Bad file descriptor 172.30.200.3:27019
Wed Oct 13 12:29:30 query failed to: mongo01:27019 exception
Wed Oct 13 12:29:30 MessagingPort say send() errno:9 Bad file descriptor 172.30.200.3:27019
Received signal 6
Backtrace: 0x51a435 0x7f7e21a85c20 0x7f7e21a85ba5 0x7f7e21a896b0 0x7f7e223296bd 0x7f7e22327906 0x7f7e22327933 0x7f7e22327a3e 0x54b506 0x660cb0 0x65a623 0x7f7e21a70d8e 0x4997a9
mongo/bin/mongos(_ZN5mongo17printStackAndExitEi+0x75)[0x51a435]
/lib/libc.so.6(+0x33c20)[0x7f7e21a85c20]
/lib/libc.so.6(gsignal+0x35)[0x7f7e21a85ba5]
/lib/libc.so.6(abort+0x180)[0x7f7e21a896b0]
/usr/lib/libstdc++.so.6(ZN9gnu_cxx27_verbose_terminate_handlerEv+0x11d)[0x7f7e223296bd]
/usr/lib/libstdc++.so.6(+0xb9906)[0x7f7e22327906]
/usr/lib/libstdc++.so.6(+0xb9933)[0x7f7e22327933]
/usr/lib/libstdc++.so.6(+0xb9a3e)[0x7f7e22327a3e]
mongo/bin/mongos(_ZN5mongo21SyncClusterConnection6insertERKSsNS_7BSONObjE+0x1f6)[0x54b506]
mongo/bin/mongos(_ZN5mongo12ConfigServer18checkConfigVersionEb+0x410)[0x660cb0]
mongo/bin/mongos(main+0x1f33)[0x65a623]
/lib/libc.so.6(__libc_start_main+0xfe)[0x7f7e21a70d8e]
mongo/bin/mongos(_ZNSt15basic_streambufIcSt11char_traitsIcEE6xsputnEPKcl+0x51)[0x4997a9]
===