Consider this simple script:
my $cgi = CGI::Simple->new;
print $cgi->header(-type => 'application/octet-stream', -attachment => 'test.tar');
print `cat test.tar`;
It does what you'd expect except with HTTPS and IE, which fails to download the file claiming the site is "unavailable or cannot be found". After many wasted man hours, we've discovered that if the site is secure and IE sees a
Pragma: No Cache header it seems to trigger the same behavior as if you had selected the "Do not save encrypted pages to disk" option.
The other strange thing is that it seems to be something caused by one of the recent security patches. It used to work fine for me before I installed Win2k SP4, but we had the same problems on other machines with differing versions of IE6. The real solution is to make more people upgrade to a browser that actually works.
Update: there's a Knowledge Base Article confirming this behavior.