Thank you, Nems. It does apply the texture when I try it, so it seems that they are indeed level blocks. Or should I say "block", in the singular, as it appears to be importing as one single large (and complex!) block rather than all the pieces that originally assembled it. I'm not sure this is going to do anything for me in he long-run, though I may tinker a bit to see if I can get it to import as all pieces rather than 1.

Also, I was very careful when I rebuilt my level using grid snapping the last time around, and I took pains not to leave any "extra" vertices, etc, and I don't see anything like that when I examine my level, so I think you're right that something is happening along the way of importing to Blender.

Can you recommend any kind of "clean-up" routines, or other optimizations I can perform from inside WED on my level? I've been trying to scale down textures and simplify architecture, but my level is really quite large because the main building is large, and I can't divide the building into different levels because it has to look like it does in real life, and because it has a very "open" layout, chopping it up would look odd and immediately obvious. When the camera swings by the main portion of the level from along the radius, the framerate drops a lot because of the complexity. I was hoping there was something I could do to alleviate this drop...