to be a great punchline here...
On the other hand, if it were my Benz lying there unconscious, I wouldn't appreciate the humor, so I'll resist the temptation
Logically, the bulb change didn't put the car to sleep (I mean, even if you shorted out the socket, it would only blow the fuse and screw-up the components on that circuit.)
Sooo... There are only two other possibilities that I can come up with:
1) An unrelated and coincidental battery/alternator-related problem;
2) A related
and shared problem which initially manifested itself in the bulb failure, and subsequently led to a complete power failure.
The second possibility seems far-fetched, but it is conceivable that a short at the taillight coupled with a faulty fuse (perhaps an incorrectly rated fuse?) caused enough heat to burn through some critical main... Again, this is a stretch, but if all else fails...
Much more likely is the first possibility. Use a simple voltmeter or multitester to check the battery itself. If it's still pushing 12 volts, then thoroughly clean the terminals and see if this helps.
PaulC's question still hasn't been adequately answered: "How dead is dead?" Do non-ignition related systems work? (i.e. Do your accessory lamps light up when you open the doors? Is the clock still running?)
If indeed NOTHING operates (and the battery/terminals test as okay), then I'd check the mains around the fusebox next.
Anyway, I'm SURE you'll figure this one out quickly. Please post the solution to this very mysterious problem when you find it!!!