Duplicate incoming messages

Since the upgrade a few days ago I am receiving duplicate incoming messages. Can anyone tell me what is going on and how to fix it. I have g-mail for e-mail

First thing to check is that the account is not added twice in Menu > Accounts.

Or maybe it is some database corruption. The best way to fix that is to remove the Gmail account from eM Client, then add it again. Let it re-sync all the messages and then see if there is any difference.