Microsoft has announced a huge patch to fix holes in the security of their software. http://ca.news.yahoo.com/s/reuters/090609/tecnology/ctech_us_microsoft_security  The more complex the code the more holes to exploit.  Perhaps it's time to have a simple operating system only!  But, with M$ not likely to ever happen... ever!

I'm usually happy to jump on the anti-Microsoft bandwagon, but this appears to be a bug with Adobe PDF.  Microsoft is just patching the parts of their software that use Adobe Reader code.  Although, why Adobe Reader has system level access in the first place is a Microsoft issue.

While the exploit will also exist in Mac OS X, it should be contained to the user level (ie, can't effect the Operating System, can't keep running when you log off, etc).  Apple will likely release a security update as well (if they haven't already)