I am having the same problem. I just submitted a bug report, but I had some more potentially relevant details.
I wanted to add that I have tried uninstalling and reinstalling Zero-k via Steam client. Problem persisted. Tried verifying file integrity: reports 2 files are bad and will be reacquired. It does so, or does something anyway since a second check of the files finds nothing. Launch game; attempt to start a campaign level or skirmish; problem persists. Close game; check files again; 2 bad files found; rinse and repeat. Still happening 3 tries later.
Guessing there is nothing on my end I can do at this time.