When you are diplo-locked, there is no one around, you cant sit around for long to wait someone to unpause for you to play and the timer is low, do the following:
- Click on the option you prefer on the diplo-screen which is blocking you. Being it "accept" or "decline" or simply dismiss, but click one of the buttons for sure.
- nothing will change for you right now and you will be forced to ctrl-alt-del the game to get out, as the game will be still paused and you will be still blocked with this diplo-screen, but if someone who can unpause the game comes after you, even if you are not around, he can login and only unpause, then immediately pauses again and leave the game, the next time you login, the game will be still paused (so you dont miss the turn) but the diplo-screen will be gone (most probably taking in to account what was your choice - to accept or deny a deal you were proposed).