Me too ... I never had this issue before either until about a month or so ago...
Speaking of weird problems, I also use Spitfie Audio and 8DIO sounds in Kontakt. These are not cheap fly by night programs... but it does this really weird thing every third or fourth session, where you record a track, but when you play it back its almost inaudible. Ive tried a gazzilion different things to fix the problem all to no avail. I used to think it was an 8DIO problem until Spitfire audio started doing the same thing. No one on the planet has ever heard of this issue either. The only work around is to reboot the instrument after every take... so I record with Kontakt strings and change to the other programs for playback. The only fix anyone has offered is switch to Mac...