Mythili, yesterday on my way home, the issue popped into my mind (don't ask why) and I though there was something not quite right here:
You are successfully opening the report, so I do not think it was actually created in CR 4 Enterprise, else it just would not work - at least that is my understanding of it. So, rather than using PSReportFoactory, I'd like you to use RASReportFactory. You can then cerate your own export button and export using RAS code.
- Ludek