After my computer did some Microsoft updates on 5/1/2015, my Windows Live Mail 2012 - Version 2012 (Build 16.4.3528.0331)

started deleting emails from Inbox and Sent mailbox on its own.

It's connected to an AT&T server account (Yahoo) using IMAP.

I then removed and re-added the AT&T email account (again using IMAP) and all of the emails returned as it re-synched with the server.

However, a few hours later (next morning) they were all gone again.

They also came back on their own and then disappeared again.

Has anyone else experienced this issue in the last few days?

Any ideas how to resolve?

I'm thinking maybe one of the Microsoft updates broke something?

Cathy