There seems to be a bug in import/blogger.php. It consistently stopped after importing 50 posts. Looking at the code in blogger.php, I noticed that MAX_RESULTS was set to 50. I experimented -- increasing it helps, up to a point around 490 comments, where things just die. If I reduce it, I get MAX_RESULTS number of posts imported.
I really want off of blogger -- happy to contribute a few bucks if it helps get this one nailed..