wu-ftp guest user configuration

I have a new installation of Ubuntu 10.04 (Lucid Lynx) and wu-ftpd version
wu-2.6.2(1) on a vintage P3 machine. I configured a guest FTP account and
found that the "dir" command returns no file list although the "ls" command
does. There is no problem with "dir" for a real FTP account. Descriptions
of dir not working that I've seen in NG archives also involves ls not
working so I haven't found any description of this specific problem. TIA for
any help.