I have a slight idea, but I don´t know if I am able to explain it.
I have that happen to me very often when I am testing apps that I am making and the issue is, when I run an app it steals the events from the Launcher (a process) then when I close my app, the key events arent returned to the Launcher so thats why is not responding. A fix for example in my case is reload the launcher from ssh.
So my guess here is that the process of connecting is stealing the OS keyboard events from the launcher.