Parsing error with Ajax update panel and time out issues.

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C#

ASP.NET

Ajax

Hi All,

I am trying to download a huge amount of data in excel sheet on a button click. This button is inside Ajax: update panel. Now what happens is that when i try to download the progress image kept inside update progress appears and stays there for a long time. After sometime than I get these two errors :
1. Sys.WebForms.PageRequestManagerTimeoutException: The server request timed out

2.Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 0

I do understand that this error comes because of asynchronous post back time outs and i kept it approx 600. But what If data is more heavy and takes more time. Moreover I created this website in 3.5 framework and now i have shifted it to 2.0 framework due to which I changed some coding too for downloading mechanism. Even I added

script language="javascript" type="text/javascript">
Sys.WebForms.PageRequestManager.getInstance().add_endRequest(endRequest);
function endRequest(sender, args)
{
	// Check to see if there's an error on this request.
	if (args.get_error() != undefined)
	{
	  //$get('Error').style.visibility = "visible";
	  // Let the framework know that the error is handled,
	  // so it doesn't throw the JavaScript alert.
	  args.set_errorHandled(true);
	}
}
</script> 

on my master page which still didn't helped me at all.
In 3.5 everything works like charm, No issues are there. To export to excel I am making use of EPPlus library. So here all I have briefed you all about my problem. Kindly help me please.