Microsoft has suspended delivering the latest Windows update to certain systems with AMD processors after reports that the update was causing the machines to crash with a blue screen of death when booting. The update contains countermeasures against both the Meltdown and Spectre attacks; although AMD systems are not affected by Meltdown, they’re vulnerable to Spectre.
Withdrawing or suspending delivery of Windows Updates is not uncommon; while there is some testing done by Microsoft, releasing things to a wider audience does from time to time unearth incompatibilities or bugs within the update. What is uncommon is that Microsoft is not merely suspending this update; the company has also outlined why.