Today build in miner was working fine but at the afternoon gave this error.
2016-10-27 18:26:46 QubitcoinMiner started
2016-10-27 18:26:46 Error in QubitcoinMiner: Keypool ran out, please call keypoolrefill before restarting the mining thread
This happens when your list of keys have been all used by the miner. Your wallet is probably locked, so it can't create new addresses for you.
You can manually top up your key pool with:
walletpassphrase 'mypassword' 1000
keypoolrefill
I think the miner should automatically refill the keypool if you mine with your wallet unlocked, I haven't checked this myself.