Microsoft Office 2011 installs Silverlight. Siliverlight is also installed by Filp4Mac. If you have previously installed Flip4Mac, and it is out of date prior to installing Office 2011, you may run into a bug where all the Apple system preference panes disappear. If you try to update Filp4Mac after installing Office 2011, you’ll get an error stating that you can’t install an old version over a newer version. The fix is to remove anything Flip4Mac related from /Library/Internet Plug-Ins/, reboot, then manually download and install the new version of Flip4Mac (don’t use the update feature).