You have to be careful when wiring up events in pageLoad(), whether using jQuery or ASP.NET AJAX's $addHandler, because it's possible to wire up multiple copies of the same event to the same element. In the previous poster's case of a Timer that updates everything, pageLoad() is the easiest way and is safe since the elements will be replaced after every Timer tick.
If you're using jQuery 1.3.x, the easiest way to resolve your problem is to use the new "live" functionality. That's extremely useful when using jQuery with UpdatePanels.