Today I installed API8 from the SDK manager, previously I only had been working with API14. After the SDK manager was done, and upon restarting ADT I got this error:
you Should Update your ADT to Latest Version by below way.
Eclipse--> Go to Help--> Install New Software --> Add--> Inside Add Repository Write Name="ADT"(as you want) and Location="https://dl-ssl.google.com/android/eclipse/" --> after loading some times you will get Developer Tools & NDK Plugins--> checked both if you want to install Use NDK as future Use or checked only developer Tool--> click Next--> Finish.
After this you can Update your SDK to latest Version.
Hope it will Help.