"Kindly let me know is it a limitation with LDAP ???"
Just because a user has been setup in LDAP for authentication, does not mean you've authorized that user to login to anything that can query the LDAP.
If this is the first server and first user you're trying to setup via LDAP, I'd suggest you go back and read the OpenLDAP documentation.
You might also want to consider a newer version of Fedora (15 was released some time ago). If Fedora's too flaky for you (or if this is not a test system), then I can understand hesitation to upgrade (in which case, I would suggest changing distributions to something a lot more stable....like CentOS).
You might want to make sure your system can actually query the LDAP before you attempt a login.
Take a crack at this guide