When multiple models are on the same project, and you go into edit one of them to add supports, the other models disappear.  The system believes they are still there, as they show on the list and the interact handles still show up when you select them in the list, but if you try and select Supports with one of the models that is not there, it tells you to select a model first.  Slice also doesn't bring them back.

I have tried going back and forth between supports and models, and it doesn't even bring them back.  Right now I have to save every model in the project then combine them later, otherwise I loose all the support work.