I can only think of 3 reasons for it not being able to open the file:

* looks in the wrong place (ie file put in the wrong place - which you say isn't the case)
* wrong permissions on the file (try chmod 777 usdir.rdm)
* corrupt file (but one would hope for a better error message in that case), maybe because uploading from Windows->Unix with a client that autotranslated linefeeds? (try re-uploading in binary mode) Or corrupted for some other reason.

/Michael