If your wallet is staking and you try to send coins that are part of the stake, it will fail.
Lock you wallet (encrypt if it's not already as always best practice), then once your coins have finished staking you will be able to do a send transaction.
I am having issues sending coins. I get "Error: Transaction creation failed" Any ideas? The wallet is currently staking but I have not had this issue before. It seems that the KTK QT is somewhat lagging as well. I get a (Non Responsive) error at the top of the window some of the time for a second. Windows 7
Keep up all the great work Dev.