Dear (Your boss's name here):
I am writing to update you on the status of (Project name here). As you may have noticed, the due date is (Insert critical date here). I first received notice of this project (Insert date at comfortable distance behind). Of course, I immediately set to work.
First, the project required a (Arcane hardware) to the (Other proprietary hardware part). That is when I discovered the (Really buggy software package goes here) had made a critical error by failing to configure the (Protocol you'll never use in a hundred years) properly, which enabled (Insert system name here) to (Make up your own error code and text).
While I was attempting to correct the problem, (Future Scapegoat) called requesting that we (Action Verb) the (Insert some aspect of the database - your boss will never know). Needless to say, this added substantially to the project's scope and forced us to extend the project's timeline.
However, my team worked overtime and weekends to accomplish these goals and had very nearly completed the project late last night, when (Insert plausible bug or virus) hit the system, causing (Description of major bollocks here). Obviously, this means we will be unable to deliver this project on time, but I promise that (Insert group's vague undefined promise) until (Specify timeframe, such as when hell freezes over).
(Regards, Sod Off, Later Tater, etc.),
(Your name here)