updated 10:05 pm EDT, Thu July 5, 2012
Faulty DRM server was root of the issue
First noticed and reported on by Instapaper creator Marco Arment, Apple has reported that it has fixed an installer issue that was causing newly-updated apps from the App Store to crash or not install properly. Users who were affected by the bug can now delete and re-download their apps from the store. In a statement, the company said the issue had been rectified, and said "we don't expect [the issue] to occur again."
The company blamed the problem on a server "that generated DRM code for some apps being downloaded," and told Macworld that the company would also remove any one-star reviews users gave applications due to the bug, which was not the fault of developers. Arment noted over 114 applications (including his own) that were affected by the issue before abandoning his maintenance of a list of affected apps. The problem was resolved shortly afterwards, less than 48 hours after it was reported.
Because of the enormous volume of apps updated through the US holiday period, however, Apple's claim that a "small number" of users were affected is likely to refer to percentages compared to the total number of users rather than a minority of affected app owners. Program creators were flooded with support tickets over the problem, many incorrectly blaming the developers as they had no way of knowing the problem was widespread. Apple had acknowledged earlier today that it was the source of the problem and that it was working to resolve the issue.