Somewhere Over the Rainbow

Message : 

An error occurred while automatically activating bundle com.android.ide.eclipse.adt (793)

......

Plug-in com.android.ide.eclipse.adt was unable to load class

com.android.ide.eclipse.adt.internal.build.builders.ResourceManagerBuilder.

Solution :

1) Start Eclipse, then select Help > Install New Software.

2) Click Add, in the top-right corner.

3) In the Add Repository dialog that appears, 

- enter "ADT Plugin" for the Name 

- and the following URL for the Location: https://dl-ssl.google.com/android/eclipse/

4) Click OK.

※ If you have trouble acquiring the plugin, try using "http" in the Location URL, instead of "https" (https is preferred for security reasons).

by Android ( http://developer.android.com/sdk/installing/installing-adt.html#Troubleshooting )