Office documents attempt to open twice

Since I upgraded to Office XP Home I have a minor technical hitch with Office 97. If I try to open an Excel or Word document from 'My Documents' rather than from within Excel or Word, I get a message telling me the document is already open. It is the same if opening from a shortcut. This does not happen with Access or any other type of document. Any ideas? This is not a big issue, but starting to become irritating.