I had to lock the wallet with the coins to prevent it staking the masternode.  The masternode should be setup to run on another machine or server allowing you to shut down the wallet with the coins.  To get it going again you will have to re-transfer the 50k coins to the masternode and restart it.  You can check the log in the masternode directory to ensure that it re-started correctly, it will say something like "masternode started you can close the cold daemon" referring to the wallet with the coins