I have just updated my android SDK tools to the newly released version (tools version 22, platform tools version 17)
java.lang.NoClassDefFoundError
I had a similar issue after the upgrade. The problem in my case was that the android-support-v4.jar library had become unchecked in the Order and Export- list. Check + rebuild solved it for me.
The error manifested itself by crashing the app when opening a dialog with a Facebook LoginButton widget on it.
Also need to make sure the Android Dependencies is checked in the Order & Export tab. Both are needed when using other library projects.
I had similar issue, following two steps fixed it:-
Java Build Path -> Order and Export tab.
Then "Project -> Clean".