Windows Explorer - Add author generaters Error 0x80004005

I have a MS Project 2007 file which I, at the bottom just over the status bar
in Windows Explorer, would like to add an author and other information to.
Well, one thing is not as supposed I think: I have added the author name in
the File > Properties dialog in MS Project but that doesn't appear in Windows
Explorer. When I try to add the an author name I get the following error:

"Apply Properties File

An unexpected error is preventing the operation. Make a not of this error
code, which might be useful if you get additional help to resolve this
problem:

Error 0x80004005: Unspecified error

Projektplan.mpp
Type: Microsoft Office Project Document
....

Try Again / Cancel"

What is going wrong?