Gmax/MakeMDL problem

I have just recently started working with Gmax. I was working last night on a scenery. I had just Exported an XML and Mdl succesfully, I then edited a few parts positions and when I tried to Export I got the following error message:
Make MDL was not found, or failed to convert the model in 'C:\gmax\meshes\Scn_1' to a .MDL file. Check your system path to ensure MakeMDL is on it.
Now I get this message no matter what source files I try to export. I have tried removing and reinstalling gmax and the Gmax sdk and still get this message. Can any one help?
Glitch
Make MDL was not found, or failed to convert the model in 'C:\gmax\meshes\Scn_1' to a .MDL file. Check your system path to ensure MakeMDL is on it.
Now I get this message no matter what source files I try to export. I have tried removing and reinstalling gmax and the Gmax sdk and still get this message. Can any one help?
Glitch