I had the alternator and battery in my 1995 854T replaced by my Volvo
dealer in October 2007.  (They've been great -- maintained the car
perfectly since new.) I left the car in my garage for 3 weeks while on
vacation and returned ~ Jan 7 to a completely dead battery.  Temperature
in the garage was 44F.  No lights, radio, etc were left on.  The service
dept at my Volvo dealer says this is not uncommon in cars equipped with
anti-theft alarm and anti-theft radio protection, and advised me to
disconnect the battery the next time I leave the car for more than 2
weeks.

Does this sound right, or do you suspect an electrical fault?

Java