Invalid MIME type(s) in list '<list>' of file type '<filetype>'
A MIME type listed in the MIME property of the specified file type is not a valid MIME type. The MIME property takes the form application/type where application represents either your application or a class of applications (such as video), and type represents a unique MIME type. The forward slash is required. You can specify more than one MIME property by separating the properties with a semicolon.
To correct this error
Double-click the error in the Task List to go to the referenced file type in the File Types Editor.
In the Properties window, select the MIME property, and correct any invalid MIME types.