Microsoft has pulled Windows RT 8.1 from the Windows Store due to unspecified technical problems.
Windows RT is for devices running on ARM chips. Version 8.1 was released two days ago, along with its Windows 8.1 cousin for x86 computers.
"Microsoft is investigating a situation affecting a limited number of users updating their Windows RT devices to Windows RT 8.1. As a result, we have temporarily removed the Windows RT 8.1 update from the Windows Store," a Microsoft spokesman said via email on Saturday.
The company is scrambling to fix the situation as soon as possible and will provide updates on the situation.
The 8.1 update is a critical one for the OS.
Windows 8 began shipping about a year ago but hasn't wowed the market due to a variety of complaints from consumers and business users alike. Most criticisms have focused on the massively redesigned user interface Microsoft calls Modern. It's based on tile icons and optimized for touch screens, but many have found it hard to master and clunky to use with mice and keyboards.
With Windows 8, Microsoft had hoped to make a run in the red-hot tablet market, where Google's Android and Apple's iOS are the dominant OSes. However, Windows 8 remains a minor player. Microsoft hopes the 8.1 update will improve perception and adoption of the OS.
Broadly disliked by users and hardware makers alike, Windows 8 RT has fared worse than Windows 8 for x86. Currently, the only tablet vendor that seems committed to Windows RT is, unsurprisingly, Microsoft. Windows RT runs on Microsoft's Surface RT tablets. Microsoft also makes Surface tablets for Windows 8.1 for x86.
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.