I am having this same problem. I have read all the documentation on rotobrush and was able to do 3 clips with no problem (awesome tool by the way). However, on my forth clip, when I hit the freeze button, the matte path disappears and the background is no longer keyed out. And as Kris experienced, it reappeared when I unfroze. I am positive that I am using the effect correctly, something is wrong.
I tried trashing prefs and restarting the computer, but no luck. I am going to open a fresh project with only that clip and see if I get any good results.
Kris, did you ever get this resolved?
-Kevin
Mac Pro 2 x 3 GHz 6-Core Intel Xeon
32GB Memory
Dual-channel 4Gb Fibre Channel PCI Express card
Dell Display (23″ flat panel)
ATI Radeon HD 5770
AJA Kona LSi SD/HD capture card
Rourke 16 TB
Flanders 2460
SOFTWARE
Mac OS X 10.6.5
FCP 7
After Effects CS5
Boris Continuum
Sapphire Plug Ins
All Trapcode Plugs
Zaxwerks Invig