I had the same problem trying to migrate from a blogger-powered blog hosted on blogspot to wordpress on my own host. For some reason, blogger choked when it came to publishing archives in the export format to my host. I ended up publishing all the files to blogspot, and then saving them, stripping out the code added by blogger for blogspot hosting, renaming them, and uploading them to my own host. That worked fine, although it took a few extra steps.