Read Tom Liston's diary entry from SANS Internet Storm Center.

To quote:

  To the best of my knowledge, over the past 5 years, this rag-tag group of volunteers
  hasn't asked for your trust: we've earned it. Now we're going to expend some
  of that hard-earned trust:

  This is a bad situation that will only get worse. The very best response that our collective
  wisdom can create is contained in this advice - unregister shimgvw.dll and use the
  unofficial patch. You need to trust us.

We agree. Read the full diary entry.

Then unregister the DLL and download and install the unofficial patch:
http://handlers.sans.org/tliston/wmffix_hexblog13.exe or
http://www.hexblog.com/security/files/wmffix_hexblog13.exe

Update: Updated the links to point to version 1.3.