Pdf grant in Directory Alias allowed through referer

Hello All,

I'm becoming crazy with this problem.

First, a brief illustration of the context.

I have a machine (next named Product) where I produce reports,
segregated according to users' profile: if you're an American user, you
can see data for US, not for Europe nor Asia.

I have another machine acting as a Portal (next named Portal) where I
want to make available to users these documents according to their
segregation. Product & Portal machines share same logic authenticating
and authorizing users.

As I can't automatically publish reports on Portal, I created a link on
Portal to a virtual directory on Product. Inside the directory on
PRoduct, I have both pdf & xls files.

Apache version on Product is 2.0.46.

Relevant configuration is:
SetEnvIf Referer "^http://Portal\.xyz\.com/" redir
SetEnvIf Referer "^http://Product\.xyz\.com/loc/" redir
Alias /loc "/var/opt/www/loc"
<Directory "/var/opt/www/loc">
Options Indexes FollowSymLinks MultiViews IncludesNoExec
Order deny,allow
Deny from all
Allow from env=redir
</Directory>

I'm receiving what I want for xls (spreadsheet opened in browser) and
generally speaking for other formats (html, txt, "foreign") while for
pdf I gen an empty page with Done on bottom left. Of course, I'm
speaking of Internet Explorer.

Curiously, Firefox correctly works (at least gives me what I want, I
don't know if its behaviour is correct).

Unluckly, Corp Std Browser is IE V6.

Am I wrong somewhere?

Has anyone an idea which is the IE setting to be tuned, or the setting
to be applied at server side to make it working as Firefox, in a
transparent way to end users?

Has someone experienced something of similar?

THanks for every appreciated comment.

Regards

Alex