Following the installation of SharePoint 2010 SP2 (KB2687453) I found that the RSS viewer web part had stopped working; the web part continually showed the loading image.
if(window._spPageContextInfo != null)
var $v_2 = window._spPageContextInfo;
var $v_3 = $v_2.webServerRelativeUrl;
var $v_4 = window._spFormDigestRefreshInterval;
The second option is to add the above script to the SharePoint master page, but I couldn’t get this to work.
The third option is to turn off web page security validation for the web application from Central Administration -> Manage web applications. Highlight the affected web application and select General Settings from the ribbon.
Turning off web page security validation worked, but I was then unable to create any new sites or lists because I received the error “An unhandled exception occured in the Silverlight application SharePoint 2010.
I have just finished testing the August 13, 2013 cumulative update for SharePoint 2010 (KB2817570) and it appears to fix the RSS viewer issue without any side affects.