When I use the Map control inside of a Telerik RadTileView it stops responding to mouse events. I found this post on their site from 2 years ago where they say its a problem with ESRI map control http://www.telerik.com/community/forums/silverlight/tileview/i-need-help.aspx It sounds exactly like the problem that I've just run into. Any Ideas???
I never tested that Telerik control but somebody in this thread gave a workaround for a similar issue with the scrollviewer. Hopefully this works in your case as well.