Make sure you do a quick search of your My Documents for "uni_ltw_sns" to make sure you don't have the old version hiding somewhere.
I always replace when I can.
What I ended up doing was moving all of my old mods to a backup directory, d/led the Director's Cut, added what I wanted from that (most of it), then added in TwoJeff's College adjuster and some of his items (vampirism and werewolf potions, wolf attraction sign, etc.) and the new uni_ltw_sns, and I haven't had a blank want since--also my load times got cut significantly.
So, barring a new blank want slot appearing, it seems to be fixed.