I am using Ubuntu for mining and I created an account about a year ago with geth (no idea which version) and mined some ether to it. Since then I reinstalled and updated geth several times and now I am not able to unlock this account to send mined ether to my new wallet.
I tried fresh install of geth 1.5.4 and just copy the keystore file - I can see the accoutnt in the geth console and I also see correct balance but I am still not able to unlock it. I also tried to install geth on different Ubuntu machine, downloaded the whole blockchain but no luck.
How can I unlock this account? Do I need to use older version of geth?