Any changes to actions or controllers results in errors or, worse, bizarre behaviour when the app runs.
For example, adding a new Action to a controller resulted in an Html.ActionLink call in a view actually calling the action.
I didn't know what had hit me...
In both cases, the problem is solved by uninstalling and re installing the t4mvc package.
Is there something I have to do to make T4 templates work with VS 2012??!
EDIT:
I forgot to mention that the project was upgraded from MVC 3 to MVC 4. It was working just fine in vs 2010 and MVC 3.