Such an issue can happen if the stylesheets are not applied to the controls. The IE8 and IE9 have limitation for number of loaded CSS files and if there are more files than 31 they are not loaded. In such a scenario there are two ways to resolve this issue.
- Add the RadStyleSheetManager to the site
- Remove all the stylesheets from the App_Themes folder, moving
them somewhere else within the site and creating there one or several
CSS files in which you link the removed CSS files one by one using
You can find more information and also the solution to solve this problem in the article Internet Explorer CSS limits
Hope this helps,