Microsoft released an Internet Explorer Security Advisory two days ago, and today security expert Moshe Ben Abu released exploit code for this vulnerability. This means that we'll likely see malware starting to use this vulnerability to infect computers pretty soon.
Microsoft recommends (as do I) that if you are running an old version of Internet Explorer it be upgraded to version 8 (you can get that for free, here). This will protect you from this new exploit.
Surf safe!