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Apple says it is investigating the issue:
We have received reports of an issue with the iOS 8.0.1 update. We are actively investigating these reports and will provide information as quickly as we can. In the meantime we have pulled back the iOS 8.0.1 update.
The iOS 8 update caused problems in some iPhones. Users complained that it disabled cellular connections and the Touch ID fingerprint sensor. However, it seems like the bugs only affected iPhone 6 and iPhone 6 Plus users.