Same problem here, but in my play-through (Necronomicon) I have finished the mission right when it appeared, but still got the “The times mission Undefendable has expired. No further action regarding this is possible.” notification.
It scared me for a while, because there was no information or notification about the mission, then I found out that I have got the technology, but the timer was not stooped properly. Next missions in the DLC seems to appear fine. No such problems in Cthulu patch.
i think this happens if you refuse to help Object 24 to obtain files from New Jericho… mission stays hidden and expires… but nonetheless, you will still progress with the DLC1 story. this mission is not mandatory to get DLC1 stuff.