Dell XPS 15Z Power Adapter Not Recognized

Hello,

I have a Dell XPS 15Z (L511Z) running Windows 7 Home Premium that I purchased in 2011.  Recently I started getting a warning at startup that the battery was no longer recognized.  The laptop worked fine with its AC adapter but would lose power immediately when unplugged.  I opened up the computer and reseated the battery connector, and this took care of the problem: the battery now works fine.

However, as soon as I fixed the battery issue a new problem started.  The laptop does not recognize when the AC adapter is plugged in.  It is clearly getting power from the AC adapter, because the battery never loses charge and the estimated time left on charge is currently 3072 hrs!

I've tried doing the following:

• Switch AC adapters.  Same result with 2 different adapters.
• Check the BIOS.  The BIOS version is A02.  Adapter warnings are enabled, charger behavior is enabled, and battery health says "This battery is performing normally."
• Check Windows battery settings.  The "Turn Off Battery Charging" box is NOT checked.
• Disconnect the battery from the computer and reboot with the AC adapter plugged in.  The computer boots fine and recognizes the AC adapter.
• Reconnect the battery to the computer and reboot with the AC adapter plugged in.  The computer boots but stops recognizing the AC adapter, even though it is getting power from it.
• Flash the BIOS.  I tried doing this but got an error saying that both the battery and AC adapter must be plugged in to flash the BIOS.  Since my problem is the system doesn't recognize the AC adapter, I'm stuck.

Any suggestions on what I can do?  I'm currently always keeping my laptop plugged in when I use it to avoid running down the battery, but that sort of defeats the purpose of having a laptop.

Thanks!