Maybe it's just my game, but I had this issue on the xbox as well. In the Brotherhood of Steel bunker, when you go to research the history of this particular chapter, the scribe in charge of records mentions there is a virus. If your science is not very high, you will have to try to isolate the virus, you have to do it three times. If it is high enough, you are supposed to be able to isolate it once, mission done. BUT the bug makes you do it all three times, and it registers the first two isolations, but not the third, and the mission can no longer be completed.
DO NOT USE SCIENCE TO SOLVE THAT QUEST!
