unable to complete version check is 99% of the time a connection problem / timeout connecting to server.
I had that a lot , and mostly i was like ftw.. my internet connection fails again lol , wich did too mostly.
may be on SE's end.. make sure you at least have allowed the ff.exe in your firewall to prevent blocking or bad connections.
Just because your internet explorer works fine and doesnt get blocked too doesn't mean the game will... something is blocking your connection for version check or causes severe lag that the check times out.. after you will get the unable to complete version check error