The Windows RT 8.1 update is back on the Windows Store, days after Microsoft took it down in response to installations that went wrong and left users with devices that couldn't boot up.
The bug affected only Surface RT tablets, which are made by Microsoft. The company estimates that about one out of 1,000 Surface RT customers who downloaded the 8.1 update were affected.
The unlucky ones found themselves unable to launch Windows after downloading the update, and instead saw an error message informing them their devices needed to be repaired and that a Boot Configuration Data file was corrupted.
On Tuesday, Microsoft said that the problem was caused by a "rare situation" in which certain devices' firmware updates hadn't been completed at the time of the 8.1 update for Windows RT. This in turn caused the update to be incomplete, rendering the devices unusable.
"We worked to quickly resolve the issue and now encourage customers to update their Surface RT devices," a Microsoft spokesman said via email.
Microsoft pulled the Windows RT 8.1 update from the Windows Store late on Friday once users started reporting the problem.
For affected Surface RT customers, Microsoft provided on Monday a way to fix the problem that involves downloading recovery code to a USB drive via a working Surface RT tablet or a Windows 7 or Windows 8 PC. The USB drive can then be plugged into the affected Surface RT tablet to fix the problem.
This is the latest in a string of setbacks that have affected Windows 8, the historic new version of the OS that started shipping a year ago but that hasn't met the sky-high expectations Microsoft had set for it.
Disliked by customers and hardware makers, Windows RT, the version for devices running on ARM chips, has fared worse than the regular Windows 8 version for x86 chips from Intel and AMD.
Microsoft has high hopes for the 8.1 update, which became available Thursday. The company is counting on the 8.1 improvements to improve the perception and adoption of the OS among both consumers and business customers.
Windows 8, with its controversial Modern (renamed from Metro) user interface based on tile icons and optimized for touch screens, was supposed to give Microsoft a boost in the tablet OS market, but Apple's iOS and Google's Android remain dominant, while Windows is still a minor player.
Juan Carlos Perez covers enterprise communication/collaboration suites, operating systems, browsers and general technology breaking news for The IDG News Service. Follow Juan on Twitter at @JuanCPerezIDG.