I think there is something a little screwball with the auto-update system in Gravity Forms.
I routinely log in and check for updates on a large multisite network I maintain. Out of the blue one day, I received a request (from a site administrator) to get rid of the notice requesting users to update Gravity Forms. I logged in, and sure enough, there was a message asking to update Gravity Forms. However, when I clicked on it, it simply gave me the following error message:
(Note: I was logged in as a super admin)
I logged in here to GravityForms.com, downloaded a fresh copy and uploaded it. The update notification and error message went away.
Is it possible that GravityForms is using it's own update system and not the one provided with WordPress? My suspicion is that you guys are using some sort of custom system which didn't alert me when I went to the regular plugin update page in the network admin. If so, it would be a good idea to change that IMO. There are some off the shelf systems for handling auto-updates which seem to work very well. I've used the system from W-Shadow previously and found it worked fairly well ... http://w-shadow.com/blog/2010/09/02/automatic-updates-for-any-plugin/