Does anyone know how to cancel a PRT COIN transaction that never went through and appears to be stuck in my PRT wallet?

On Feb. 8 I tried to send 256,289.9981 PRT from my PRT wallet (version particle-qt-8.7.3) to my Coinedup.com PRT wallet.

I've since sent 5 PRT and 2 PRT and they've went through successfully but not the transaction for 256,289.9981 PRT.

Here are the Transaction details:

Status: 0/unconfirmed
Date: 08/02/2014 11:03
To: PhCJXkduRc5MFZwq28sGXFf6uoNkdVUvR1
Debit: -256289.998 PRT
Transaction fee: -0.0001 PRT
Net amount: -256289.9981 PRT
Transaction ID: 04e11b831e76aee0994d6ed1ea37f66e8f0112aa57c3b936da26449c21fca041

Any help would be greatly appreciated.