I'm new here and to iToo software in general ...
I can set up a 3D tree using Forest Lite, and with a mr Area light cast a nice shadow no problem.
However in my architectural model, with a mr Area light the trunk shadow is not cast.
My renderer is mr. The light shadow is default -- raytrace shadows.
I don't have any planes set to not receiving shadows.
I am in 3ds Max 2013.
I've had the same problem in test files, but the shadows cast well with mr Area lights as well as the Daylight system.
I thought I had the problem solved, but it re-appears in my final working file however.
I turned off exposure controls and removed all HDRI to reduce possible issues.