Vlad suggested something was wrong with LDAP and my colleague Thomas diagnosed that opendirectoryd was crashing. All true.
It happened again tonight and Vlad found a way to restart opendirectoryd (in Terminal.app):
sudo launchctl stop com.apple.opendirectoryd
Which restarts opendirectoryd.
I’m none the wiser on what triggers the opendirectoryd crash at wake from sleep. But I’m glad this works when the crash happens.
Update: The above doesn’t always work. Actually, it may have worked just once. Since then, I’ve experienced silent opendirectoryd crash, and no sudo worked, neither some kill -9. Only a restart can fix it.