Being told a document is already open by me and asking if i want to make a copy???

Does anybody know what would cause a document to give the message:

C:/Documentsandsettings/test.doc is already being used by john smith. Do you want to make a copy?

I get this everytime I open any document. The pc is on a two computer network, I have not already opened the docuemtn before to make it say it.