Recently I had a problem with ScriptManager on a WebForms site where I was also using the ScriptManager.
Suddenly my ASP.net validators stopped working client-side and on Firebug I could read this error:
ASP.NET Ajax Client-Side Framework Failed To Load
Crap… what am I doing wrong here!?
It seems that Rounting messes with the .axd files script manager generates so we only need to tell the routing to ignore those: