When the outbound URL has certain characters in it, the JavaScript will fail. Internet Explorer throws an error with "unterminated string constant". Firefox does not give an error. I suspect that it's the "@" symbol in this example:
Example:
<a href="<a href="http://www.flickr.com/photos/20862202@N05/34522186582/" onclick="javascript:pageTracker._trackPageview('/outbound/comment/<a href="http://www.flickr.com/photos/20862202@N05/3452083282/');" title=