1)Disband your fleet.
If your income is still negative, (check the income tab) try one of the next items.
2)Sell as many resources as you need to in order to get out of debt.
3)Get people to use positive dineros on you (this has a very limited affect)
If the above methods fail...
4)Reset your empire. You`re done. Cooked. Debt is one of the valid ways to die in this game, so always be careful of your economic situation.