Depending on your version of Internet Explorer (i.e. 11) you may need to perform the following fix.

Add the following script to your master page.

<script language="javascript">
/* IE11 Fix for SP2010 */
if (typeof UserAgentInfo.strBrowser !== 'undefined' && !window.addEventListener) {
UserAgentInfo.strBrowser=1; } </script>

Note: And should be added right above the </body> tag on the master page (in your case v4.master).

Please refer to the article http://social.technet.microsoft.com/Forums/sharepoint/en-US/5a81a95b-a4d0-4e6c-a8c4-5602698e5a32/windows-81-and-ie11-critical-error-object-doesnt-support-property-or-method-addeventlistener