[Plugin: Jetpack by WordPress.com] Error: Jetpack deactivated due to invalid header??

I was alerted to an available update for the Jetpack plugin, so I went ahead and clicked to update the plugin. I got the notification at the top of the screen telling me Jetpack had been deactivated and now I can’t find the plugin anywehre, not in my list of all plugins, or the list of inactive plugins, or anywhere on the dashboard…what gives? And how do I sort this?

http://wordpress.org/extend/plugins/jetpack/