ADB issues on Galaxy S3 and Windows 7 - installed but not working?

Question

I'm trying to develop for my Galaxy S3 using my Lenovo U510 Ultrabook with Windows 7 64 bit. I have tried the following tutorials and then some:

http://www.dkszone.net/setup-install-adb-android-debug-bridge-windows-7 windows 7 adb driver Samsung galaxy S3

My phone is being listed as an ADB device in the Device Manager:

but when I run "adb devices" from the command prompt, I get the following:

And nothing shows up in my AVD Manager:

I've tried this same thing with several different drivers and cables, and get the same results. Any ideas as to what's going on?

Thanks for any pushes in the right direction.