Than your server is likely reporting the wrong information for at least one server variable.
In calendar.pl the line:
$Template::CGI_URL = $AdminConfig->get("calendar_url") | | $ENV{'SCRIPT_NAME'} | | $ENV{'REQUEST_URI'};
will need to be changed and in calendar_admin.pl the line:
$Template::CGI_URL = $ENV{'SCRIPT_NAME'} | | $ENV{'REQUEST_URI'};
You can try reversing the $ENV{'SCRIPT_NAME'} and $ENV{'REQUEST_URI'} variables to see if that might correct the problem.
If that doesn't correct it, you may need to contact your host's support to see if they can correct it on their end of know of a work around. Those values might even be able to be 'hard coded'.
JMO
Dan O.
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