We have been testing your scene with the same configuration (3ds Max 2014 SP5, FP 4.2.5, Corona Alpha v7.1), but we are unable to reproduce your troubles here. As you can see on attached screenshot, we can create a Forest object using the "floor ground rug" object as a base surface.
The only strange behaviour we have noticed, that there is an unusual delay when creating the forest_templates layer (caused by 3ds Max's Merge operation). As we don't have installed some of plug-ins used in the scene (Quad Chamfer and RandomisedFaceIds), would you please test it having these temporary disabled? Thanks in advance.
Regarding the forum issue:
Our forum was moved to a new server some days ago and recently we have noticed that behaviour also. Sorry for any inconvenience caused, we are working on it.