Joshmc - 4:06 pm on Dec 10, 2010 (gmt 0)
Webmaster central blog confirmed it as a bug
The indexed URL counts for Sitemaps that you have submitted in Webmaster Tools may be showing zero (0) indexed URLs for some sites. We are aware of this issue and are looking into it; you do not need to take any action. This will have no effect on your site's crawling, indexing, or ranking / performance in search results. Thank you for your patience as our engineers look into this issue.