I wanted to follow up and let you know what I finally found out. There were a couple of issues.

• I had to install CGI::Session in my local lib, and a couple of the files appeared to be truncated during the upload. I re-uploaded the files, and finally got an informative error message.
• Only one specific directory is writeable in the hosting environment; this is not documented anywhere. When I called support, they told me they didn't even have perl/cgi available on Windows hosting. I had to point the support person to their own docs online to show otherwise. When I put the session files in the correct directory, everything worked like magic.

Thanks again for your valuable tips.
digger