"Anti-virus vendor Trend Micro Inc. has spotted a Trojan in the wild attacking Windows users via the image rendering flaws patched by Microsoft Corp. two days ago.
"The Trojan, identified as TROJ_EMFSPLOIT.A, causes the "explorer.exe" file to crash, causing the taskbar on unpatched Windows machines to disappear."
Not exactly the effect reported, since it was a toolbar rather than the task bar that went AWOL; but suspicious enough to suggest that it might be worth checking out the patch. Internet Explorer is critically dependent on the affected file.
Windows 2000, WinXP and Server2003 may be affected. The Trojan found in the wild is apparently a "proof of concept" thing, and doesn't do real damage; but the potential for serious stuff is there.