[Plugin: WordPress Importer] Import fails, outputs "Array()"

I have several blogs in an MU installation that I’m trying to combine into a single blog. However, importing posts from other blogs into the main blog does not appear to be working. The result ends up outputting

Array ( ) 1

I’ve set IMPORT_DEBUG to true as specified in the blow post, but I don’t see any further information:
http://ww.wp.xz.cn/support/topic/plugin-wordpress-importer-wordpress-importer-problem-all-posts-author-become-admin?replies=9

http://ww.wp.xz.cn/extend/plugins/wordpress-importer/