woody

not an answer to your question but you might want tomake sure that your render flags are the same as your display flags.

I've found that you can use the Task Manager in windows to kill a render sequence. Ctl-Alt_del , choose task Manager, go to the processes tab, find the mantra process, and End Task. One problem is there's no way to identify the rener process in the Task Manager, so if you have more than one render going and only want to kill one, you're out of luck.

just some things to check -
merge sop sometimes converts vertex uvs to point uvs, that can mess up yr shading in places. Fix this by applying a vertex sop after the merge ( on the affected group only) and substitute in the vertex uvs from before you merged using the second input and “Add texture” with $MAPU2, $MAPV2

merge sop doesn't like it when some inputs have explicit normals and others do not, make sure all inputs have normals by using facet sop and “compute normals”

the above may not be your problem at all, but i thought i'd point it out.