In my case I put it in the index page. It works perfect with firefox but there is a problem with IE7: most of the times doesn't work, but a few times runs depending from the page you are trying to reach the index.
The html text for the popin is:
<div><img src="images/stories/fotos/show28b.jpg" border="0" width="600" height="100"/></div>
The URL is www.ceciliagauna.com
Noy the plugin is disabled.
Any suggestion will be appreciated.
Thanks!

Its difficult to troubleshoot random behaviour without at least seeing it live

IE7 is one nasty bitch to work with...