Problem with locked index.htm

I designed a site in DW and have one user making content changes to the
site using Contribute 4.

They can modify all pages except index.htm. Contribute says that I have
the file locked.

I have tried check the file out and then back in several times. The file
shows on my computer with a lock and no icons on the server.

permissions for this user are to be able to change/add/delete any file.

What am I overlooking - alex