"Cancel" button in apk download notification only works sometimes

During my testing, it seems that the "Cancel" button will work if the download has not yet begun. That is, the progress bar is indeterminate, probably while we make an initial connection to the server to find out how big the apk is. Had a quick search, could it be related to: http://stackoverflow.com/questions/3168484/pendingintent-works-correctly-for-the-first-notification-but-incorrectly-for-the ?

Seems like the code to add the cancel action to the notification looks fine, so unsure what it could be. Any ideas @paresh?