try to put this line in your receiver's intent-filter.
<action android:name="android.intent.action.ACTION_EXTERNAL_APPLICATIONS_AVAILABLE" />
If your application is installed on the SD card, you should register this to get the android.intent.action.BOOT_COMPLETED event.
Updated: Since your app is using alarm service, it should not be installed on external storage. Reference: http://developer.android.com/guide/topics/data/install-location.html