Hmm, that was an odd one. I removed all the faces from the body and trunk meshes, but when I re-filled the holes after selecting all edges a few faces just wouldn't map properly. I had to individually fill each hole, though I don't understand why this worked! I am afraid I don't understand enough about how Anim8or generates faces to understand the problem.
There were also a few points in the Trunk mesh that were duplicated, which resulted in malformed edges, I have corrected these and restored the mesh. This can happen if merging points in two meshes without removing edges that would duplicate as a result of the join. Such duplicates would require 2-sided polygons, which cannot exist, so the mesh is broken at this point (ie the points do not merge). This can be difficult to spot, since the points are in the same place in all axes and the mesh looks contiguous. In any case, the attached file seems to be ok now, at least joining the car body and trunk solids works without crashing Anim8or.