I replaced the battery in my 2006 audi a8-- now trunk button on drivers door not working--an mmi screen and radio works for 1 min. then off Help!

SOURCE: i can't open the lid

I had a similar problem with my TT Roadster and it was a problem with my central locking system, it temporarily disengaged after a minor incident with the rain while my top was down. Anyway for me it was simply a matter of time before the system reengaged it's self it took maybe a week or so, but to get around the problem, behind your passenger seat there is a storage compartment, pull the lever in the storage compartment to open the trunk, once in the trunk on the left sidewall of the trunk there is a seamless square open that square and there is a black pulley in there, pull on that and your gas tank should open. I hope this help.

SOURCE: 2005 audi a8 trunk + upgrades for ipod integration

I had exact same problem, but what I found out was a three step solution to the problem.
1) The trunk lock above the trunk lid tself - sometimes looses coiling retention for the lock to work properly, which in effect does not properly lock wrap around the pull down electronic unit located in the body of the car/trunk that catches and pull the trunk lid down SOLUTION: check and make sure lock is works properly. you cab check by opening trunk and locking it with remote key, then pry the lock with a screw driver to see if it unlocks or stays locked

2) The motor catching unit in the body of the car/trunk that catches the lid and draws it down can be off balance (sitting too low to catch the lock (upper trunk lid with lock) to pull it down and stay locked. Have a mechanic - Audi preferrably, check the positon and allignment to adjust it, so it can catch trunk lid and lock to stay locked. HOPE THIS HELPS!

SOURCE: I have a 2000 Audi TT Quattro. Never had a problem

I wouldn't be surprised if those are ran off vacuum, Check the vwvortex.com