I think this happen because of the request timeout. most probably your web site set request timeout for 1hr.
Because of the timeout response will not getting to the page. (registers script will not rendering)
please check the web.config file following section and modify accordingly
<system.web>
<httpruntime executiontimeout="3600">
</httpruntime></system.web>
And please check the following also
http://codebetter.com/petervanooijen/2006/06/15/timeout-of-an-asp-net-page/[
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