IPN - getting 404 errors

[FinallyInSeattle]

Paypal's IPN is getting nothing but 404 errors when trying to connect to http://www.mywebsite.com/administrator/components/com_virtuemart/notify.php.  Has anyone found a solution to this or are we all forced to manually update the status of our orders?  Do I need to change permissions?  The url itself is odd, it doesn't follow the standard "index.php ..." convention.

I'm running Joomla 1.5.14 / VirtueMart 1.1.3.  Thanks in advance for any assistance!