Apple has posted KB 306043 Mac OS X: Some applications may not open after QuickTime 7.2 Update with directions on dealing with issues resulting from the latest QT 7.2 update.
In addition, to the solution the Entourage Help Blog posted in the article iTunes 7.3.1 and Quicktime 7.2 Updaters cause problems for Office on 7/12, directions include steps to use Terminal commands to resolve the problem.
[If you are having problems with the update prebinding failing see the MacFixIt article When Office apps won't launch: a fix for update_prebinding]
