Posting this here and on Corona forums - but the rendering difference without and without Forest Pack is night and day.
I'm trying to render a lawn, with the lawn turned off no problems at all. Turn the lawn on and it takes an age to kick into action, then goes into parsing for ages, then I can't cancel out of it until parsing has finished about 15 minutes later. Corona 8 (latest official release, no dailies) and latest Forest Pack.