Hi Ashwin,
First, make sure Crystal Reports Designer and BI Enterprise are on the same patch level.
Next, ensure all required firewall ports are open for communication.
If that doesn't help, assign a port (between 6402 & 6500) for the RAS Server and open this port for communication in the Firewall.
Please have a look at the Admin Guide here:
SAP BusinessObjects Business Intelligence platform 4.1 – SAP Help Portal Page
-Abhilash
