GetFirstDocument problem with collection

I have a database where getting the firstdocument in a collection fails. My code is:Set DocColl = Doc.Responses

Set ResponseDoc = DocColl.GetFirstDocument

DocColl has a count > 0, but ResponseDoc is always NULL if I declare ResponseDoc as a NotesDocument, but if I dont declare it, the debugger shows it with a value of [MAILFILEACTION]. This app is not a mail file.

If I cut and paste the documents into a clean database, the problem goes away. Anyone come across anything like this before?