SSRS in SharePoint 2010 integreted mode throws error after 3 minutes



Hi,
Gettting below errror if SSRS report takes more than 3 miuntes in SharePoint 2010 which in integrated mode
Message: Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code
returned from the server was: 503
Line: 5
Char: 62123
Code: 0
URI: http://ap-msbi-dev.csintra.net/ScriptResource.axd?d=X5UTS6t4bTLxH1hI3Q-raGfj2vRa74U7NuIytr25CmFxyPB6lBtbuihyELTMWQoy-
O716bFOsKQQ3h4tukJL54Ec5fT73va9QFcwTNTfeUP9cVXks4P2B0U4QbMLzsbS8R4vlKUHKeA7O8OL-kWJvt3-RAk1&t=2e2045e2Please any suggest on this. Report works fine if it
takes less than 3 minutes.

Thanks,

Manjunath