System crashes when trying to set 2nd and 3rd voices invisible

I am trying to juggle the artificial harmonics into working properly by setting the actual written notes as muted and by inserting a 2nd or 3rd voice to play the actual note, which I want to set as invisible, so that I can both hear an see the artificial harmonics. Whenever I try to set the 3rd voice (high f) as invisible the whole program stops working. I tried it with the f being 2nd voice as well and it does the same. The 1st voice however can be set as invisible with no problems arising. I guess it has to do with the coexistence of many voices, but i don't get what's happening. By the way, this happens both before and after I have set the 1st voice as muted.
Any idea what i can do to work around this?