Excel 07 error "file cannot be found... check your spelling or try

[Redwren]

When someone else in the company has a file open, and someone else tries to
open the same file, we get the following error:

Path/document name.xls cannot be found. Check your spelling, or try a
different path. In older versions, you would get a "read only" message
when trying to open a document that someone else was in.

I have unchecked the "Ignore other applications that use DDE" box under
options and we still get same error message.

HELP!!!!!!