You can see this news http://www.crn.com/sections/microsoft/microsoft.jhtml?articleId=193100291 , that explain the problem.
Other links about this news:
http://www.betanews.com/article/Visual_Studio_Incompatibility_Hits_Vista/1159382996
http://www.dotnetnuke.com/Community/BlogsDotNetNuke/tabid/825/EntryID/1145/Default.aspx