OK, so I've been playing Fallout 4 for the last few days, on a windows 7 PC. Runs rather slower than it really ought to in places, but it's been working. Today the game froze up on me while attempting to exit a building, and now I can't get it to launch at all. I just get a black screen for a second followed by a CTD. Restarting computer, validating the files etc. has no effect. I haven't tried a full reinstall as I'd really prefer not having to redownload the whole thing if it can possibly be avoided.

The last session was only a few minutes long, and the only thing I can think of that I did during it, and hadn't done previously, was to turn on the dialogue subtitles. Turned up a couple of threads mentioning similar symptoms, but those seem to be something to do with changing the graphics settings or messing with the ini files, and I haven't touched those.

Anyone got any ideas why this suddenly stopped working, and if so how do I fix it?