Have receive this error couple of times while working with share point web services ,
"The file you are attempting to save or retrieve has been blocked from this Web site by the server administrators."
Outsource the incorrect URL caused this , however the description of the error makes it confusing
Correct URL should be http://web.domain.com/sites/sitename/_vti_bin/lists.asmx
URL by error occurred http://collaborate.kronos.com/sites/datadump/vti_bin/lists.asmx - notice missing "_ " here