Error 52

I get the following error on build intermittently: <!--more-->

Error 52 It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level.  This error can be caused by a virtual directory not being configured as an application in IIS. C:\Work\…\web.config 98 Frontend

I get it infrequently enough that I never remember the fix for it.  I always Google it and come up with the same links – they all imply it’s because of a problem with some configuration.  For me it’s not a configuration problem.  If I delete the \obj directory and rebuild that fixes it.  Go figure.