I've searched for this problem but can't find anyone else experiencing it.
I was using Roto Brush for a while today and everything was working as expected. I Roto Brushed about 20 frames, just doing touchups where necessary. However, after a while, Roto Brush just stopped responding to new strokes. I could not add or remove from the mask. I've tried flushing the RAM and then restarting AE but the problem persists.
I'm using After Effects CC on Windows 7 64-bit with 16GB of RAM.
I made a screencast to show the problem. You'll see me painting to add and remove from the mask on a couple of frames. Roto Brush looks like it's going to do something but then nothing changes in the mask. Youtube link to the screencast is below:
http://www.youtube.com/watch?v=qhTh2z6ohT4
What am I doing wrong?