Password Protected administrator causes problems

Hi,
My Joomla 1.5, administrator folder is password Protected with.htpasswd and .htaccess files. Lately, I am having troubles with documents seller. It is not displaying the link to download the files after PayPal payment and it isn't sending the e-mail with the link and attachment to the client.
I think it is the fact that this directory is protected that is causing the problem. I temporarily removed the protection files and refreshed the page on the web site where before the link to download the link wasn't displaying and the link appeared.
I did a second test without administrator folder protected, and the e-mail was sent to the client and the link displayed on the page after paypal payment.
How can I have the administrator folder protected in this way without it causing problems to documents seller?
thank you for your help.
Best regards
Fernando

I m curious about that, have you find any way to solve it ?

Thanks