Trying to import a private key into bitcoind
Without anything in the log, it's difficult to day. But here are a few suggestions what could try to find out the cause of the error:


Do you have write permission on the wallet.dat file in your .bitcoin directory?
Is the wallet locked with a passphrase? Then you need to unlock it (would probably give another error message but worth asking).
Did you set the disablewallet option either in command line or configuration file?
Is your wallet possibly locked due to a -reindex operation?