Starting on August 3, Microsoft began rolling out the Windows Phone Dev Center, part of which includes a different backend infrastructure, a change that has now led to these errors. More specifically, the new infrastructure has created an issue with the digital certificates that are used to sign apps, preventing users from properly installing or updating recently-published apps.
Microsoft has concluded, however, that the issue only seems to be affecting phones that were upgraded to Windows Phone 7.5 from an older version of the OS. Those with models that were shipped with Mango should not have any problems. It has also been determined that the error only seems to be affecting a small percentage of the apps in the Marketplace, the most significant ones being New York Times, WhatsApp, and Translator from Bing.
Microsoft says that it knows what’s causing the issue and is already working on rolling out a fix, but until that happens, app publishing will be halted. In the meantime, the company said that users that encounter an error while installing or publishing an app should wait for a fix to be issued rather than uninstalling any apps, because they will lose their saved data for the apps and it’s unlikely that they will be able to reinstall them until the problem is fixed.