I'm having the same issue, I use rotobrush, it calculates a span, and the green lin extends over my whole clip, exactly as I want. I hit freeze, and the actual matte disappears, there is no selection information, the entire frame is comlete with no part masked out. If I hit freeze again to unfreeze it, all the work comes back, the footage is masked/matted and the span information is there with the green line again.
I was hoping that freeze would freeze the calculations of the span, preserve the matte.
Weee need much more info - footage used, system specs, exact version of AE, otehr stuff.
I think I figured it out. You have to set you work area to the part that you want to freeze.