I have created a custom module that opens up a page in the admin overlay.  Upon going to that page, a PDF is generated and the link to the file is displayed on the page.  I created the link using the l() function and gave the link a target attribute of '_blank' to open in a new tab/window:

    l('Click here to download your PDF file.', $f_url, array('attributes' => array('target' => '_blank')))

The link looks like it is generated correctly:

    <a href="http://xxxx.com/sites/default/files/custom-pdf/xxxx_4.pdf" target="_blank">Click here to download your PDF file.</a>

But when I click on it, it opens in a new window, but somehow the overlay fragment is tacked onto the end of the URL in the new window address bar:

    http://xxxx.com/sites/default/files/custom-pdf/xxxx_4.pdf#overlay-context=test.html

And the browser throws up a dialog box with a title of "Adobe PDF Document" and a message alert of "This operation is not allowed".

If I click this link from a non overlay page, it does exactly what it's supposed to do: open the PDF in a new window.

I'm not exactly sure what's going on here.  How is the overlay fragment being appended to the URL ... and how can I prevent it?