We are seeing samples of the VML exploit that are coded to include browser / OS detection, and are able to trigger working exploits for Win 2000, 2003 and XP. Some reports indicate that client-side anti-virus is not sufficient to protect, some AV apparently only catches the VML exploit code once Internet Explorer writes the temp file to disk, which can be too late. The exploits versions seen so far usually pull and run an EXE file, but adding patterns for new EXE payloads is an arms race the AV vendors can't win. If you have the option, we suggest you use the work around of unregistering the DLL as indicated in our earlier diary entry.