Conditional comments and r.a.d ajax

We use the Telerik r.a.d. controls here, and I encountered a problem that was causing alot of problems. On a button click using ajax, I'd get crazy moving of several screen elements. If turns out since I was using conditional comments and they were being lost on the callback. So I had the following in the header (which by the way is how you can conditionally have different stylesheets for IE):

<!--[if lte IE 7]><link rel="stylesheet" href="ie7.css" type="text/css" charset="utf-8" /><![endif]-->
<!--[if lte IE 6]><link rel="stylesheet" href="ie6.css" type="text/css" charset="utf-8" /><![endif]-->

Anyway setting EnablePageHeadUpdate="false" in the RadAjaxPanel fixes the problem.