This is a problem with the Project Engine in DAE 2.95 or 2.96. This error is usually followed by Program error which prevents a save, quit, etc. The only way out is to force quit or restart the Mac.In this scenario, is important to save the session before doing any scrubbing, since the only work-around to avoid this error would be to avoid scrubbing backwards.DAE 3.1 and later resolves this.