Our umbraco 7 installation is giving errors when trying to make a datatype that uses one of the following property editors:

• Umbraco.CheckBoxList
• Umbraco.ColorPickerAlias
• Umbraco.DropDown
• Umbraco.DropDownMultiple
• Umbraco.DropdownlistMultiplePublishKeys
• Umbraco.DropdownlistPublishingKeys
• Umbraco.UploadField
• Umbraco.RadioButtonList

I get a pop-up message that says:

Server error: Contact administrator, see log for full details. Failed to save data for data type id 1197

Checking the log table in Umbraco gives me nothing to work with, as all it says is "Save DataTypeDefinition performed by user"

Checking the network tab on my developer toolbar I see a post being made to /umbraco/UmbracoApi/DataType which results in a Server 500 error with the following response:

{"Message":"An error has occurred.","ExceptionMessage":"The given key was not present in the dictionary.","ExceptionType":"System.Collections.Generic.KeyNotFoundException","StackTrace":" at System.Collections.Generic.Dictionary2.get_Item(TKey key)\r\n at Umbraco.Web.PropertyEditors.ValueListPreValueEditor.ConvertEditorToDb(IDictionary2 editorValue, PreValueCollection currentValue)\r\n at Umbraco.Web.Editors.DataTypeController.PostSave(DataTypeSave dataType)\r\n at lambda_method(Closure , Object , Object[] )\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.<>cDisplayClass13.c(Object instance, Object[] methodParameters)\r\n at System.Web.Http.Controllers.ReflectedHttpActionDescriptor.ActionExecutor.Execute(Object instance, Object[] arguments)\r\n at System.Threading.Tasks.TaskHelpers.RunSynchronously[TResult](Func`1 func, CancellationToken cancellationToken)"}

How do I fix this?

-Ferdy