I had the same issue. Please try the following in eclipse
Help –> Install new software
Then choose “Android Developer Tools Update Site – http://dl-ssl.google.com/android/eclipse/” from the drop down list and update the ADT
IF THIS THROWS ERROR Like this
No repository found containing: osgi.bundle,com.android.ide.eclipse.adt,21.1.0.v201302060044-569685
Modify http: to https:
Sample : https://dl-ssl.google.com/android/eclipse/
And then update ADT. This method worked for me.