If you are using Bitcoin Core 0.12.0 or 0.12.1, you can go to Help > Debug Window and click on the Console tab. Then type in the box at the bottom
abandontransaction aaddeaa91cc7ed77b58044fa274cd6abaa0dd46b90f42a5bf05ab052775e0f28
If it doesn't give you an error, you should then be able to respend the inputs spent by that transaction.
So I did that, and didn't get an error. The full amount is back on the main screen. The transaction is still there though, is it always going to be there? I haven't resent anything and now I'm not even sure I want to or even should. Is there any way to clear the transaction from the wallet?
Thanks.