Hey there,
I'm running the newest builds of the import files and am having problems with import. I had a user import 837 blogs and it crapped out at 400. I figured it might be due to size but when I tried again with a smaller file it still crapped out.
I installed a quick standalone copy of wordpress and imported directly to that and it went perfectly. Any idea what might allow it to work ok on wordpress 2.0.5 but have problems on wpmu?