I'm having this problem:
To duplicate it, try adding one of each Telerik control to a page, then open the page in IE and see if all them appear correctly. I have a page that has several different Telerik controls (RadAjax, RadTooltip, RadTabStrip, RadDate and Time Pickers, RadEditor, etc). If I count all of the WebResource.axd references that IE 8 is making, it's over 30. If I remove a couple Telerik controls, then the remaining controls get their style back.
They all appear perfect in Firefox 3.6.8, Chrome and Safari, so I know it's an IE 8 issue. Is Telerik aware of this? Is there any way around this?