Cannot complete this action – error when adding a ContentType to a list

Today I got a nice error from my SharePoint development box after I tried to add a certain Content Type to a list. Cannot complete this action. Please try again. at Microsoft.SharePoint.Library.SPRequestInternalClass.AddField(String bstrUrl, String bstrListName, String bstrSchemaXml, Int32 grfAdd) at Microsoft.SharePoint.Library.SPRequest.AddField(String bstrUrl, String bstrListName, String bstrSchemaXml, Int32 grfAdd)Cannot complete this action. Please try again. at […]