While I don't have an immediate cure. I'm pretty sure you're dealing with an HTTP header issue.

In other words; Apache is intervening with an authentication type header, when you were attempting an image type header.

HTH, if I can think of something more concrete (a solution), I'll post back.

--Chris

#!/usr/bin/perl -Tw
use Perl::Always or die;
my $perl_version = (5.12.5);
print $perl_version;