Hi Val - does this happen with any kind of model or just one particular model that you are working on?

Like for example if you export a box out from MoI into the other program, does it say the box is a solid or not?

If it's something to do with your particular model I will probably need to see the model in order to give you some advice on it, you can either post the 3DM model file here or if you want to keep it private e-mail it to me at moi@moi3d.com

What specific errors are you seeing in the other program, does it really say that it is not a solid or does it complain about something else in particular like some tolerances or other issues?

Also what happens if you re-import the file you just saved back into a new session of MoI ?

- Michael