I'm getting this in both DNN 8 and 9 installations.
Here is the error from the event log:
FriendlyName:Bring2mind\DMX
ModuleControlSource:DesktopModules/Bring2mind/DMX/Dispatch.ascx
AbsoluteURL:/Default.aspx
DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke
ExceptionGUID:66804463-2242-434f-9f30-1b79736cbd34
AssemblyVersion:8.0.4
PortalId:0
UserId:1
TabId:131
RawUrl:/Admin/Laws-Administration?Command=Core_Edit&CollectionId=0&EntryType=File
Referrer:
http://www3.grandfamilies.../Laws-Administration UserAgent:Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.87 Safari/537.36
ExceptionHash:Vhf7zw7kts1+Lcch8Nytkw==
Message:Value cannot be null. Parameter name: format
StackTrace:
InnerMessage:Value cannot be null. Parameter name: format
InnerStackTrace:
at System.String.Format(String format, Object arg0, Object arg1, Object arg2)
at Bring2mind.DNN.Modules.DMX.Edits.EditEntryPB.ᜁ()
at Bring2mind.DNN.Modules.DMX.Edits.EditEntryPB.ᜄ(Object A_0, EventArgs A_1)