Hi,
Just wanted to report that I too am having this issue with Gravity Forms 1.6.4.5 and WordPress 3.4.1:
http://www.gravityhelp.com/forums/topic/notifications-are-coming-through-incomplete
I have rewritten all my forms to not use numerical fields, which was a PITA. I didn't want to lose the numerical data that had previously been submitted, though, so I retained those fields, even if I'm not using them. Yet the email notifications are still incomplete.
These forms used to work fine in an earlier version of Gravity Forms. I really hope this functionality is restored soon.
-Ken