I already posted this here, but it is important enough for me to repeat. Sorry to those who will get this more than once!
If you are running Windows, especially XP, you should check your computer to see if it is vulnerable to the infamous Windows MetaFile vulnerability.
If you are not vulnerable, it means you have either installed one of the previous patches or else you’ve used Windows Update to get the official patch (make sure you are using Internet Explorer for the MS Update page).
If the tool tells you that you are vulnerable, make sure to follow its instructions on getting the correct patch.
I just ran the MetaFix tool from Steve this morning, and am now good to go.
[UPDATE: The tool is now called Mousetrap, and so I've updated the links to point to it instead.]