This is probably not helpful, but I get that message when I try to start up PA under Linux with an invalid language in my system. The odds of you having that are rather small though. Did you change any settings on your computer or install new things? In any case, maybe the logs contain something useful. You can find those in "%LOCALAPPDATA%\Uber Entertainment\Planetary Annihilation\log". On a typical install %LOCALAPPDATA% will be "C:\Users\<username>\AppData\Local".
