When you pull changes from Tortoise HG you need to then run Tortoise HG > Update to update you working copy with the changes.
Then you need to rebuild the solution, then you need to visit the /Setup/Default.aspx page
You should not be deploying the .cs source code files to production, they are not needed, you should publish a compiled version to a local folder, do some cleanup of files, then deploy the compiled files to production maintaining the custom machine key (and any other customizations) in your web.config file
Hope that helps,
Joe