Probably after the fact, particularly after BB's very knowledgable explaination, but I was wrestling with this problem with sharp edged models also, particularly artefacts from bevels. With strictly hard, straight edged objects where no smoothing is required you can completely disable smoothing by setting both crease angle to zero and smoothing to off. Either one or the other by itself won't work and poser will still smooth the object.

Another method I've found that works if you want some smoothing and still maintain the appearance of hard edges requires that you increase the poly count of the object somewhat by creating a series of micro bevels around the edges of the objects. I like this method because you maintain the appearance of hard edges, get the specular effects that bevels produce, and don't have to spend alot of time tweaking crease angles or deal with unwelding. This method is illustrated below by a couple of preview renders. the results are the same and better with full on firefly renders...