I received some mails today and found a post on techcrunch and the launcherpro blog that Google has locked down GMail so that my app email widget (and also many other apps) stopped working with it. You can find a technical explanation here.
That’s really sad news because it means that we have to wait for Google adding support for third party apps to access gmails 🙁
— ADDED LATER:
I just noticed that GMail has set the access permission to “signature”, so also rooting and installing my app as system app won’t work!!
You can find a modified Gmail.apk which has the permission restriction removed here: http://forum.xda-developers.com/showthread.php?t=1199598
Instructions on how to modify any version of Gmail to work with the widget
http://koxx3.wordpress.com/create-your-own-modded-version-of-gmail-allowing-content-sharing-with-external-apps/