Some PCs can't boot after latest Windows 11 security update, no fix in sight —mostly affects 24H2 and 25H2 versions

Some Windows 11 PCs are unable to boot after the latest security update, affecting versions 24H2 and 25H2. Users have reported encountering an "UNMOUNTABLE_BOOT_VOLUME" error, leading to a black screen with a restart message. Previous issues from the update include PCs not shutting down or hibernating and Cloud-based apps malfunctioning. Microsoft has released emergency updates for some problems but has yet to address the booting issue. Users are advised to uninstall the latest security patch as a temporary fix until a solution is provided.