I sent coins without realizing I did not update the wallet, now I updated but the transaction is shown as unconfirmed and my wallet balance is minus the transaction amount. What can be done?
Next time invest in a coin that doesn't hard fork every week.
Seriously, can I do something or are the coins lost?
They're not lost, don't remember what you have to do exactly though, I think you can simply download the latest Darkcoin QT and open it up instead of the old one and delete the blockchain? Don't do that right away though wait for someone else to confirm.