Apple has updated Aperture, its software for pro photographers, to version 3.1.1 (http://support.apple.com/kb/TS2518). The update improves overall stability and performance.
For example, Aperture 3.1.1 fixes an issue that could cause iMovie ’11 to stop responding while scanning the Aperture library for video clips. It also addresses issues that prevented the Aperture library from appearing in the Media Browser of other applications.
You can obtain Aperture 3.1.1 via the Software Updates component of Mac OS X’s Systems Preferences app. It requires Mac OS X 10.5.8 or higher.