I've been using clueTips on my site for a little while. I found that when used on links, the links are no longer clickable. eg. If you create a link to google.com and put a clueTip on it, the clueTip will work, but you can't click the link to go through to google.com.

So far I've tested in Firefox 3.5.8 and Safari 4.0.3

Even the demo on the clueTip site behaves this way. See http://plugins.learningjquery.com/cluetip/demo/ example 7.