For those who are having problems...
Download the new 1.6 update released on 24/December at the website (http://www.starcoin.info/download.php)
If you get the checkpoint error and you have already updated to the new client for some reason or another corruption has occured in the chain...
To be able to fix you need to either redownload the blockchain from scratch or copy the chain from another working client and start the client with the command line option "-rescan".
Don't forget to backup your wallet before beginning this process just in case, and also don't forget to use the checkwallet/repairwallet command inside the debug console once the process is complete to confirm that your balance is corrected.
If anyone needs a hand feel free to drop me a pm.
Regards,
infin.
Did this, still says checkpoint too old. Will try again.