Are you sure all servers referenced in the report are still online? If you've changed database connections on the report, I've seen Crystal store a reference to the old one even when there are no active usages. If the old server is offline, Crystal still tries to connect to it when loading and will hang for a long time. We had a report that used to load in seconds start taking minutes right after an old test server was powered down. Powered it back up, it loaded instantly again, even though all the connections to it were seeming removed. We wound up totally rebuilding the report from scratch.
I found it using Sysinternals TDIMon, it showed connection attempts and timeouts coming from Crystal.