From Photoshop News.com
Apple has posted a TechNote for users of OS X 10.5 Leopard with Time Machine and Aperture. By extension, it also applies to Adobe Photoshop Lightroom users as well.
Issue or symptom
Running Time Machine backup or restore operations while Aperture is running may lead to inconsistencies in the Aperture database.
Products affected
Aperture
Mac OS X 10.5 Leopard
Solution
If you use Time Machine with Leopard, be sure to set Time Machine to exclude the Aperture Library from automatic backups. To do so:
Open Time Machine.
Click the Options button.
Click the “+” button in the Do not back up window.
Use the resulting file browser to navigate to the location of your Aperture Library. The default location is ~/Pictures/Aperture Library (where “~” represents your home folder).
Click the Exclude button.
Click the Done button.
Note that this means that your Aperture Library will not be backed up by Time Machine. Be sure to manually back up your Aperture Library.
Until Next Time,
Jarrod Michael
Executive Producer
The Digital Artistry Blog
www.digitalartistry.blogspot.com