The error occurs during three possible conditions. If Members/test.file or NonCGI/test.file exist, or if emailfile.cgi doesn't exist.
Its probably that the emailfile.cgi file doesn't exist, so I would hop on over to
http://www.ubbcentral.com/downloads and get the 5.x rebuildmems script and run it.
If that doesn't do it, you may want to delete the test files noted above.
You should probably consider upgrading as well
Kristi Horn
Infopop Customer Support
Visit our Support Area!