In previous posts I talked about the inaccurate results received when using the SPSiteDataQuery with more than 10 document libraries or lists. http://www.sharepointblogs.com/smc750/archive/2007/07/24/spsitedataquery-limited-to-10-document-libraries-or-lists.aspx
This bug has now been confirmed with the release of KB article 946484 on January 16.
This bug will also affect the Microsoft.SharePoint.Publishing.ContentByQueryWebPart. There seems to be no work around for this webpart because it does not have the ability to set its scope to multiple lists.