If you are getting an error message while installing or updating an app in your Windows Phone you have to hold on for a day or two. Let us explain you in detail what is at the background.
Originally there was a problem discovered with the digital certificates used to sign in. Due to this problem some phones were having trouble installing apps for the past 3 days. Though the problem has been fixed temporarily, Microsoft officially has confirmed that it will take a day or more until the problem is fixed permanently.
As specified in Windowsteamblog by Mazhar Mohammed, a Windows employee:
We fixed the digital certificate problem and last evening resumed publishing new apps and updates. It will take a day or two for the repair to fully deploy and newly-published apps to begin appearing in Marketplace again.If you experienced errors, I want to emphasize that you don’t need to do anything to start downloading new apps or updates once the repair has finished rolling out.
Behind the scene: Why this happened?
The issue came out while deploying the Windows Phone Dev Center, which includes a completely rebuilt backend infrastructure. The issue was with phones that have been updated to Windows Phone 7.5 and not with the same pre-installed OS. The bug affected 100,000 apps in the Marketplace, which also includes New York Times, WhatsApp, and Translator from Bing—all of which recently issued new updates.
If u are a developer u need not worry as your app will continue to go through the certification and publishing workflow normally. Yet it is to be noted that all published Apps remain available in the marketplace. We wish all the server fixes are applied pretty quick. We’ll keep you posted about this issue!