updatepanel gets refreshed

I have updatepanel on my page.
on click of button my server side code takes more then 10 min. for processing. but my updatepanel get refresh after 10 min. and it gives resquest.pagemanager error

i tried to set AsyncPostBackTimeout="1000"

But it does'n work for me

can anybody help me
i m using ajax 2.0 extension 1.0 & VS 2005