This place is dead, you can never get help in here.
Patience, young padawan...
Anyway, my guess'd be that the costumes you've uninstalled were for a different CaC race. That error message basically says, that one of your races .bcs file has 1000 partsets already, so you'll need to reduce the amount of partset entries in that bcs specifically. My suggestion would be getting genser from eternitys tools thread and dragging each races bcs over it one at a time. Then look inside the xmls that were created to find out which one has a partset with idx="999" and then uninstalling costumes that you know add to that race.
This post was made from free-roaming, 100% chlorine-free bleached, CFC-free and non-genetically-modified bits.