First, you have my sympathies. It sucks to have to work late on short notice like that :(

Now, let's bring on the flood of questions! Did you solve the problem, or was it one of those things where someone in the know has to take a look at it manually? Was the customer polite, or was he a total ass? And...do you get overtime because of stuff like that, or does your employer adjust your future schedule to make up for the extra time?