[Plugin: Advertising Manager] Adding a second Ad on my Header breaks the website!

Hi,

I’m wondering why manually adding a second banner on my header template is breaking my website (meaning that the web doesn’t load at all).

I want to have a full width banner on the very top plus a standard 468×60 banner a bit after it.

First one shows right with this code:
`<!– Banner : Top-Leaderboard –>
<?php advman_ad(Top-Leaderboard); ?>`

So I decided to use a similar line for the second:
`<!– Banner : Top-Banner-468×60 –>
<?php advman_ad(Top-Banner-468×60); ?>`

… but then my whole website gets blank, empty!
(Editing it’s source it’s just white!)
The ad is a simple one:
<a href="http://www.sponsor_website.com" target="_blank"><img src="http://www.my_website.com/wp-content/banners/banner_468x60.gif"></a>
It looks fine on the preview but I’ve got to be doing something wrong.
What am I missing?
Thanks in advance!