I have a W2k3 server running IIS6 and MVC2 (.net 4).
Right after the iis starts, everything works ok, the site runs fine. Extensionless urls work ok.
After a certain period of time (maybe of inactivity) the server stops working and starts to send 404 errors to the client.
As soon as I restart de application pool, everithing goes back to normal and the site is up again. The thing is, I shouldn't be restarting the application pool every few hours.