After upgrading to 1.6.5 (and applying the upstart workaround), when I start mongodb I see:

Fri Dec 10 00:35:18 MongoDB starting : pid=12278 port=27017 dbpath=/var/lib/mongodb 64-bit
Fri Dec 10 00:35:18 db version v1.6.5, pdfile version 4.5
Fri Dec 10 00:35:18 git version: 0eb017e9b2828155a67c5612183337b89e12e291
Fri Dec 10 00:35:18 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
Fri Dec 10 00:35:18 [initandlisten] waiting for connections on port 27017
Fri Dec 10 00:35:18 [websvr] web admin interface listening on port 28017
Fri Dec 10 00:35:18 [websvr] couldn't unlink socket file /tmp/mongodb-28017.sockerrno:1 Operation not permitted skipping
Fri Dec 10 00:40:59 [initandlisten] connection accepted from 10.203.61.189:47342 #1

Not sure how to release the socket so that the webadmin can start.