Whilst working on a recently upgraded SharePoint 2010 site (database attach upgrade) I attempted to modify an existing web part. As soon as the page went into edit mode I was presented with the following SharePoint error: “One or more field types are not installed properly. Go to the list settings page to delete these fields.”
This appears to be a random bug which seems to occur with some sites after they have been upgraded and is related to a list called ‘Relationships List’.
To fix this de-activate the SharePoint Server Publishing Infrastructure Feature in the sites settings, delete the Relationships List and re-activate the feature.
