When storing I use a Battery post cutoff switch and a Battery Tender.
Your DME relay may have gone out. If you do a search you will find info on removing and resoldering the cold/cracked joints on the relay's circuit board. This will help in many cases. BTW, it is located right under the front of the driver's seat.
Carrera owners are best off carrying a DME relay around.
Add: Here's a recent thread on relay repair:
http://forums.pelicanparts.com/showthread.php?t=370070&highlight=dme+relay
Also, welcome to the board!