OK, so the tx somehow wasn't relayed from your node to the network. You can clear the current tx pool state by stopping the daemon, deleting poolstate.bin in Aeon's blockchain folder (~/.aeon/ on *nix systems, C:\ProgramData\aeon\ on Windows) and starting the daemon again. Also probably you'll need to delete the wallet cache file (the file without .keys extension) and opening the .keys file again with simplewallet which will reconstruct the wallet cache file. You'll see your funds used in the failed transaction back to your balance, and you can try sending them again.

Make sure that your network connection is stable when sending money.