I didn't know about that thumbnail image thing, but I tried it just now and it didn't crash. Took a while to load the images though, maybe it's a ram thing? Or video driver, like criss says--see if you can update your drivers? When you're exporting, is it a procedural that doesn't export? It wouldn't surprise me if procedural textures wouldn't be exported, it would have to be turned into an image texture in the process because procedural textures in bryce are not the same as the ones in blender. Image textures should export just fine though.