From 10.7.5 Lion, MacOSX stopped supporting old SAMBA Protocols. Due to this i am unable to access the NAS which is running old SMB Server.
Here the fix details :
Create a File /etc/sysctl.conf with the following contents and restart the Mac.
# Re-enable smb support for my old LinkSys NAS200
# Maybe make NAS faster?
Now, MacOSX Lion can able to access the SMB server. Also the property delayed_ack=0 increases the throughput as well.