Bitcoin wallet rescan
Of course, you can't create or destroy coins with this, and the money still winds up at the right destination. However, the typical user isn't going to know how to restore an old wallet and rescan the block chain to get his bitcoin client back to working condition.
It might be a good idea to patch this before some enterprising person with excess time on their hands (cough) makes a cloned transaction echobot. You can also find a decent explanation, which (hopefully) does not require a deep technical understanding of the Bitcoin implementation, of transaction malleability (that's how this bug was eventually named - beautiful name!) here