I am having trouble meshing some geometry I have imported from Pro/Engineer.

I get the error ACIS error 5000 : coincident face_face_ints with different body vertices

The geometry seems to mesh with tets ok but i cannot split the volume so that i can have greater control over the meshing. Trying to export as Iges does not work either.

Can anyone help me get round this and/or explain exactly what the error message means?

As I suggested in a previous post (http://www.cfd-online.com/Forum/fluent.cgi?read=7041) you should check for duplicate vertices, that has helped me several times. Tet meshing sometimes works with such degenerate geometry but it either generates a sliver or even a cell with negative volume.