Ah, that old chestnut.
midnight phone call from your network monitoring service saying "hey, looks like your domain controller's down-down..."
Jump in the car, drive to the office, hit no less than 4 construction sites turning 93 into one lane.
Get to the office, discover the primary T1 is soft down so the failover to the backup line never happened.
Manually down the interface so everything fails over, open a ticket with the ISP's NOC, set up laptop, put on music, and wait for a callback.
Fuck tonight right in the ear. *sigh*
Edit: was there until 2am, nothing got fixed but they were going to roll a truck in the morning.
So here I am again waiting for said truck.