Recently we posted an article on this:

http://blogs.msdn.com/b/selvar/archive/2010/07/12/report-builder-2-0-3-0-errors-out-with-the-operation-has-timed-out-when-previewing-a-report-saved-in-report-server-takes-more-than-10-minutes.aspx

HTH!

Reporting Service India Support Team.

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