Data nodes won't reconnect after 7.1->7.2 upgrade (no replies)

I just upgraded from 7.1.18 to 7.2.4 and my data nodes won't reconnect to the cluster.

I shut down the entire cluster, upgraded the managers and started them up, upgraded the data nodes and tried to start them up with this command:

/usr/sbin/ndbmtd --defaults-file=/etc/ndb.cnf -n

The manager logs are being spammed with:

2012-03-20 19:46:37 [MgmtSrvr] INFO -- Node 10: Node shutdown completed, restarting, no start.
2012-03-20 19:46:37 [MgmtSrvr] INFO -- Node 13: Node shutdown completed, restarting, no start.
2012-03-20 19:46:37 [MgmtSrvr] INFO -- Node 12: Node shutdown completed, restarting, no start.
2012-03-20 19:46:37 [MgmtSrvr] INFO -- Node 11: Node shutdown completed, restarting, no start.

Both 'show' and 'all status' show no data nodes connected at all.

Any idea what could be wrong?