When I launched interface tonight it informed me to download a new version, which I duly did. I did not uninstall the old version.
I launched interface and it loaded fine. However I decided I wanted to change my avatar, so I went to preferences and decided to do away with Evil Philip. I suspect this is the source of my problem.
Not long after that Interface crashed. When I relaunched Interface, it crashed. Since then I have a uninstalled Interface and reinstalled it, on launch it still crashes.
I suspect my Windows profile has some settings in registry as I have noticed that my avatar on my PC and Mac are different, suggesting some values are stored locally, but I simply cannot get Interface to run now on my Windows 8.1 PC.