Apple has released a supplemental update to OS X 10.7.3 that addresses problems some people have had when trying to use Time Machine to restore their Macs.
The update is a 24.55MB download that is available via Software Update, but can also be downloaded at the update's Web page and manually installed.
The update requires OS X 10.7.3 to install, so if you are running prior versions and are thinking about updating, you'll need to first update and then check Software Update again or manually apply this patch to ensure your system is fully updated (applying the patch a second time will not hurt your system).
If you have upgraded to OS X 10.7.3 and plan on doing any restorations with Time Machine, such as migrating to a new system or wiping your hard drive and restoring from a backup, then be sure to first install this update.
The update appears to install a single file in the /private/tmp/ directory called "TimeMachineUpdatePayload" that contains a single dash in it, which may be used to force an update of the Time Machine backup and spur the proper behavior of Time Machine.
While it may seem like an odd suggestion given the nature of this update, do be sure to back up your system before applying this or any other update, though once you have applied the update, use the Time Machine menu to manually back up your machine again.