浏览器在上载繁重文件时挂起

Hi i'm doing a PHP/Javasript file upload using the plugin jquery.form.js which basically uses XHR2 for upload. But while we upload the files the browsers basic functionalities like scrolling, clicking kind of functionalities are not working. So i am greatly confusing on how to fix this. Any help/suggestions on this would be grateful.Hi i'm doing a PHP/Javasript file upload using