Microsoft says it has figured out what caused some Surface RT machines to shut down unexpectedly while downloading the free Windows RT 8.1 update, and has restored the update to the Windows Store.
The company said Tuesday the problem occurred when previously released updates were still being installed while the Windows RT 8.1 update was being downloaded. For about 1 out of 1,000 Surface RT owners who downloaded the 8.1 update, that caused the machine to shut down and become inoperable.
Microsoft has offered a way to revive the unit and complete the update using a USB drive. The solution requires using a separate computer.
On Tuesday, Microsoft also began selling its latest models, Surface 2 and Surface Pro 2.