Does anyone know how to back up the nxt wallet ? I didn't find the back up wallet option like on other wallets.
You needn't back it up, it's all stored in the blockchain. But don't lose your passphrase, your passphrase is your wallet.
They had a manditory upgrade to 1.4.5. Did cost me 24 hours and couldn't get it working. Took all my coins out of nxt wallet. Try again when bugs are gone.