I spent some time debugging a SL3 application with VS 2010 in IE9 beta today and noticed a few quirks. Sometimes when launching the Silverlight app in VS it fails to load in the browser, but refreshing with F5 tends to fix the problem. Also, there are sporadic scripting errors that pop up a debug dialog - these also seem to be fixed by refreshing the page. Has anyone run into these problems and found a fix?
EDIT: My most prevalent error is: Error: ASP.NET Ajax client-side framework failed to load.