Check to see that you have the most recent version of the plug-in.
Use the LR plug-in manger to "check for updates" or check inside the Nik EXE by launching it manually.
I reinstalled Nik, downloading their latest version. It is still highly unstable. Now the plug-in closes sometimes, sometimes not. And usually there is a lag of about half a minute before it closes. Very strange. I'm working on a Mac, but the way.
In the plug-in settings dialog, try turning off the GPU acceleration and see if that helps.