Center button on key died.

My key has been working fine but requiring closer and closer proximity to the car until it quit entirely. So I cut it open and checked the battery: only 1.2V. Replaced the battery and now it seems the middle button is dead. The front button (disarm/unlock/windows down) works fine and the rear button (hatch glass) is fine. Distance to activate is greatly improved but can't arm the alarm or lock the car remotely, (can't arm the alarm at all).

The car is a 2001 325iT.

Why would the middle button quit after battery replacement? Thinking I must have damaged some circuitry while cutting the key open or replacing the battery but it all looks ok. There's one piece with some fine copper windings that may have been minorly disturbed - the windings don't look 100% "tidy". Could that have done it? The middle button clicks fine and I tested it without the cover with same results.

I have done the reprogramming sequence several times. No response while holding down the front button and clicking the middle one which leads me to believe the middle one is at fault.

If I can't get this middle button to work, is there a way to arm the alarm without it? Otherwise I will have to cough up $$ for a new key.

Thanks for your thoughts!