ASP.NET MVC 3 on IIS gives 403 after period of time, requires app pool restart

I have an ASP.NET MVC 3 site running on Windows 2003 / IIS 6. Everything works fine for awhile (days/weeks at a time), and then I start getting 403 errors. T开发者_如何学JAVAhis happens if a user goes to the root of the domain, as well as going to any other full route. Restarting the app pool fixes the 403 and everything goes back to normal, but I am trying to figure out the root problem so it does not go down and require a manual app pool restart. Any ideas?

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Here are the same symptoms - Asp.Net-MVC application dying

I do experience the same issue with IIS6/MVC3. It seems to be somehow related to routing...