I'm having this issue as well, for the first time. I am guessing that it has to do with something on the Minecraft server side, as it affects all servers I try to join. I suppose waiting a while will make it solve itself. I have tried the following to fix it.
1. Restart client
2. Force update
3. Delete entire .minecraft folder and update
4. Redownload client
5. Restart computer
6. Restart router
7. Disconnect from router and reconnect
None of them fixed the problem. However, I AM able to play from the browser client, but when I try to mine a block it goes to the escape menu for some reason.