Like any new tool, there are bugs, and Google's Webmaster Central tools, including their powerful Sitemaps tool, seems to have its share of bugs. Two different reports come from WebmasterWorld with possible bugs in the tool over the weekend.
The first report was that there are Many Strange Reports in Google Webmaster Tools - Sitemaps. And I quote:
As of midnight Friday, G Sitemap tools is showing "no pages are indexed" for 11 domains that were just fine Friday afternoon. A site: search returns the same miserable results I've had all week after getting whacked in this latest data push.
Page with the highest PageRank has changed and shows www.example.com/?PHPSESSID=1c9eb347d770d93ad076f8ae3106319a although googlebot is filtered not to see sessions and if it goes to page with session server will return 404 error. This filter is up from start of November.
The second report says that there are Completely wrong common words in GWT?. I'll quote again;
When I look at the keywords for the new site in the Google webmaster tools, the list is packed full of words... that have nothing to do with my site! They seem to be about cruises, sports, casinos, and various commercial and financial matters.
WebmasterWorld administrator Tedster believes that this is a reporting bug only and possibly old data is being presented in just the reports.