page request manager parser error exception

See more:

C#

Javascript

UpdatePanel

This exception is thrown when I use update progress with update panel in my Ajax tab panel enclosed in master page. I didn't use trigger in update panel, because it would disturb my UI, I have around 4 buttons, of which 3 buttons are dedicated to download xlsx file using response object. Any suggestion is appreciated.. I am using asp.net 4.0 with c# , the update progress is being displayed, a few seconds later this exception is raised....