I did the following: walletpassphrase my password 600 true. Then i got the following message: {"code":-1,"message":"walletpassphrase \nStores the wallet decryption key in memory for seconds."}.
But the locked sign right below (a yellow lock) doesn't change and my wallet is still locked.

update:
Using your instructions I unlocked the wallet. But fort the instrcutions I need to close all wallets for salvagewallet method
See: https://github.com/eagleflies/noblecoin/wiki/Importing-private-keys-from-old-wallet.dat-using---salvagewallet-option

What is best step after unlocking the wallet?

Thanks