I've recently switched hosting providers at the company I work for. Instead of being able to use wildcard mapping or the .mvc file extension mapping, I'm left with .aspx.
The premise of this exercise is easily explained here: http://www.asp.net/learn/mvc/tutorial-08-cs.aspx, specifically Listing #3 under the Hosted Server section.
While this is fine for a default MVC1 project, I've currently implemented Phil Haack's Areas v1 prototype with Steve Sanderson's CreateArea extension method located here http://blog.codeville.net/2008/11/05/app-areas-in-aspnet-mvc-take-2/.
To make the Global.asax change from Listing #3 in the first link (phew), you need to modify all routes to add the .aspx extension. The same goes true for .mvc.
I followed ...