Ajax文件使用会话时上载不正常的行为

I have just implemented an Ajax File Upload control that uses a progress bar. I am a little confused. When i use the control on pages that dont use sessions, the progress bar with no problems will show the user the actual progress of the file being uploaded from 0%,1%,2%,3%.......% to 100%. Now when i move this control onto a web page that uses a session, this session stores the user information such as screenname, email, etc... the file uploads with no problems but I have just implemented an Ajax File Upload con