So starting lat last night on both my Nexus 7 and my GSM Galaxy Nexus the Inbox and Sent Labels for only 1 of my Gmail account's started showing 'No Conversations' as if I had archived all the mail in my inbox and my sent folder. The browser version works just fine, even on the Nexus 7. I also am not getting email notifications for this account.
The odd thing is that i have 3 Gmail accounts on both the devices and it is only happening to 1 of the accounts, the same on both devices.
I have tried to clear cache, but did not want to clear data unless absolutely necessary as I do not want to have to reconfigure anything if I don't have to.