I'm glad to find out that I'm not the only one having this problem.  I was having the same problem with both the skirt and the top.  When you add morphs you get a black line and either the morphs go crazy or it won't render at all.  I found that if I add morphs slowly and don't put them all in one place, you get the problem to stop.  For instance, if you need a 0.8 "Amazon" or "Voluptuous" morph in the skirt to get it to cover your character and you get the line, dial the morph back to 0.6 or whatever until the line disappears, then start adding morphs to the thighs, hips or whatever until you get the results you want.  In other words, spread the morph out over the separate body parts.  It sounds stupid, but it works without having to buy any scripts or utilities.

Hope this helps.