1. All the lawyers are gone. That's usually when the sh*t hits the fan and everything goes to hell. More so if they are all gone on a firm retreat and are too inebriated to help by phone or e-mail. (Yes, I have been there.)
2. A lawyer actually says "thank you" for something that doesn't really deserve thanks. Not a guaranteed warning sign of Bad Things, but certainly a good possibility.
3. It's the last day before you go on vacation for a week. Double points if you have a flight to catch that evening. Triple if it's overseas. That's why I always have my suitcase packed and in the car my last day before vacation.
4. You come in one morning to several dozen new e-mails from your attorney(s), all sent in the wee hours of the morning.