If you have not heard, there is a very serious Internet Explorer Zero Day exploit making it's rounds. How serious? Serious enough for Microsoft to put forth an Out-of-Band patch for it. This is very much related to the Google China network compromise that has been in the news recently - this was one of the exploits leverage that gave hackers access to Google's network. Since then the exploit code has shown up in various places on the Internet where more blackhats and criminals have gotten their hands on it.
While initially an IE 6 exploit, proof of concept code now exists that can target IE 7 - IE 8 appears to be somewhat protected if DEP is still enabled on the system.
This exploit is serious enough where the French and German governments have issued public advisories to it's populace to use an alternate browser like Firefox or Opera.