What is the best way to recover from an accidental double-spend? Came across an issue where I was given the message:

"Error: The transaction was rejected.  This might happen if some of the coins in your wallet were already spent, such as if you used a copy of wallet.dat and coins were spent in the copy but not marked as spent here."

It appears that the 2nd amount was deducted from my total balance even though it still sits at 0/unconfirmed status days later even though the unconfirmed transaction has disappeared from the blockchain.

Any suggestions?  I've also installed Python and tried running a script provided by someone else (within Windows 7) and cannot seem to get the script to run properly.

Any help is greatly appreciated.
Apparently to get the RPC command removeprivkey you'll need a build of the Bitcoin client which includes pull #220 (which has been merged into main).  The latest version (currently v0.12.1) contains this feature.

Here are the instructions to do that:

Step 1. Back up your wallet.  You are performing wallet surgery here, ... and doing things you might not have intended.

Run Bitcoin as a server, e.g.,


  $ ./bitcoin-qt -server


Then 

If you've encrypted your wallet you'll need to open it for RPC


  $ ./bitcoind walletpassphrase [passphrase] 1000


Then


  $ ./bitcoind dumpprivkey [bitcoin address]


Then copy and paste the private key it provides.
Then


  $ ./bitcoind removeprivkey [bitcoin private key]


Then close bitcoin-qt.

After that


  $ ./bitcoind -rescan