There are several ways to solve the problem of browsers caching AJAX requests. You can use a 'cache buster' parameter, or you can set the response headers server-side. This article discusses these two options.
If you use the Microsoft filter CSS property to allow support for an alpha transparent PNG on an element, any links directly within that element are not clickable (in Internet Explorer 6 only). The problem is explained and a solution put forward that will make your links clickable again.