Did you launch the wallet with -walletbroadcast=0? If yes, then you should launch it normally without any arguments as the wallet won't broadcast any transactions to the network and your transactions won't be seen by others.

You can follow BitMaxz advice and launch it with -zapwallettxes which will remove all the unconfirmed transaction. You will have to wait for the transaction to be dropped by the nodes around the network and you can send a new transaction.