Ray shadow issues after importing from SketchUp

I imported a hallway that I built in SketchUp into Blender, added a floor and a light, but shadows don’t want to work right.

There is ONLY one difference in the settings between these two pictures. In one, ray shadows are off. In the other, ray shadows are on. Everything else is identical

(the cube is there just to make it clear that it’s only the SketchUp objects that are having a problem).

I tried changing the scale of the image, to see if that would fix it (because after import, SketchUp objects are huge in Blender), but that didn’t work. Making it smaller made those dots you see a little more dense, but it was still all dithered up (if that’s what’s happening).

I’m running Blender 2.49b.
Win XP SP3
Video Card (old, I know): ATI Mobility Radeon 7500

WITHOUT RAY SHADOWS:

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs285.snc4/40571_427711346117_214452616117_4837409_3641569_n.jpg

WITH RAY SHADOWS:

http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs123.ash2/39513_427711336117_214452616117_4837408_5436481_n.jpg

Haven’t done it in a while, but I used to get a lot of duplicate geometry when importing a model built in Sketchup, and what you’re getting looks like overlapping geometry. Have you tried removing doubles?

Ah! That fixed it. Yeah, had about 63,000 duplicate vertices . . . yikes. Something to look out for in the future.

Thank you so much!