1script - 4:12 am on Apr 28, 2010 (gmt 0)
Same here - most sites in WMT show 0 indexed URLs. In many cases I have multiple sitemaps and one index sitemap per site. Some individual sitemaps show 0 and some show a few dozen (150 I think is max), all on the same site.
Traffic is not affected as far as I can tell, so this much have been a reporting fluke.