samba - Aug 2012 - smbc_opendir() is failing with "Connection timed out"

Hi,
I'm using samba-3.6.7.?
smbc_opendir() is failing with "Connection timed out" error if I give
hostname as argument. For example smb://hostname

But it is working fine if I give sharename. Ex smb://hostname/sharename
It is working fine if I give IP address. Ex : smb://IPaddress

Any clue?

thanks,
-Kish