hmm..you didn't say, but I am guessing Xbox360...
And if that is true or any other console, check your console date and time settings...the war table missions base their completions off of real time and they use the consoles time clock to do this. So if something resets or alters the system time clock, then it effects the time left in quest, and most times this is due to the xbox360 losing track of time when shut down, as it gets older.
That is not new, I'm not sure why it happens but, all you need to do is start the game, then change your system clock to a time when the mission will be finished. Return to the game briefly, then set the clock back to the correct time. The mission will be done and, all will be fine again.
If this is a console, do a hard reset (power off with the power button to reset the clock, this should clear it.
