SSRS reports Time out

Hi, recently we had an issue with SSRS 2005 with one of our applications and had to remove and reinstall and reconfigure it. everything is working fine, except for certain large reports. when we run them i let it run and after approximately 35 minutes it ceases running with a message on the screen ” Report processing has been canceled by the user”. using subscriptions to drop the report file to a share failed with the same errors. tried running the report at off hours still same issue.
This report used to run before we reconfigured SSRS and all the config files have exactly the same settings.
any help is greatly appreciated.