Sounds like your file path is not valid.
You might try using "file:" & Get ( DesktopPath ) & "bfsv3sp.mer" in a set variable step and then typing the name of the variable into your File Reference dialog instead of the text you are using. That guarantees a valid file path to your user's desktop.
If you are certain that the path is valid, make sure that the current user has "write" permission to that location and make user that your user account permissions do not need repair.
Thanks for looking into my question.