When I checked the active script instances on my 360 save (long story on how I did that) it was the same four or five scripts repeated several hundred times, resulting in around 1300 active scripts. If you are on console, try to avoid these quests if you can. The effects are not immediately apparent and scripts seem to continue being created even after the questline is finished.
As a side note, this issue may also have something to do with curing vampirism or changing your face. I have no way of proving this, but my issues arose after I did this several times.