You can update the adt from here
You might need to update the software source for your adt update
Go to eclipse > help > Check for updates.
It should list the latest update of adt. If it is not working try this
go to eclipse > help > Install new software
Click on add
add this url : https://dl-ssl.google.com/android/eclipse/
give it any name.
It will list the updates available- which should ideally be adt 20.xx
Eclipse will restart and hopefully everything should work fine for you.