After my JB update, but not immediately after, I get intermittent pop-up errors saying Unfortunately google.services.gapps has stopped, with 2 buttons, Report and OK. Also the same with gmail stopping.
I thought I might be able to delete my google account and re add it, sign in and then resync, but on my Settings page, where it used to say Accounts & Sync, it now only says Accounts, and I can't find any way to unsync and resync.