At this point you need to stop sending more transactions until the previous ones settle. The problem here is that you have sent a transaction that used coins that you just received but were not confirmed before sending again.
Maybe someone has a better solution for this, but I would just wait and next time don't use unconfirmed coins as inputs for sending.
But. but. but... The coins have been in my wallet for a month at least.
I had an issue in my wallet two months ago when it showed un-confirmed balance.
As per the wallet support people, I emptied my wallet to a new one and then created a new wallet where I sent my coins. That cleared the unconfirmed balance.
But now a month later when I want to send my coins to an exchange I run into this problem.
Maybe it is a wallet problem.. How to fix it? I dont want to lose my 12 BTC!