Well, Microsoft patch tuesday has delivered a whole host of critical security patches to MS Windows, Office, Explorer, and others. Several of these are actively exploited and can lead to some stranger in a far away land running whatever software they want on your computer.
So go get your updates now.
Here is some more information, and there is a patch for MS Powerpoint on Mac as well:
http://www.theregister.co.uk/2006/06/14/ms_june_patch_tuesday/
http://www.microsoft.com/technet/security/bulletin/ms06-jun.mspx
