In an effort to do some basic operations on lists and list items (namely delete a list item), I noticed I'm getting a 'Page cannot be displayed error.' I've had a look around other areas of my site and for some reason majority of the OOTB application pages and modal dialogs give me the same error!?
My custom application pages work.
I've tried looking at the logs (nothing there that's unexpected or wasn't there prior to this behaviour) and I've tried looking over all of the services to check everything's started as it should be.