Yesterday evening, some wrong information made the round where it was said that Microsoft has remotely locked Windows Phone 7 smartphones which were previously unlocked with ChevronWP7. However, as a matter of fact, Microsoft hasn't sent any OTA kill-bits to the affected Windows Phone 7 devices but the Windows Phone 7 devices itself have automatically asked Microsoft if they were supposed to be unlocked. The ChevronWP7 developer team has explained in a blog post that Microsoft told them before "that after a short amount of time - approximately two weeks - phones unlocked via ChevronWP7 would revert back to their original locked state".
This is due to a routine-check of the Windows Phone 7 OS where the phone connects to Microsoft to verify the installed certificates. Since the ChevronWP7-unlock requires the installation of a certificate, Microsoft is responding to the device that this certificate isn't valid any longer and therefore Windows Phone 7 automatically reverts to the previous state. If this happens (and users are neither informed that Windows Phone 7 contacted Microsoft nor informed that anything was changed) homebrewed and side-loaded applications won't open anymore but returning a misleading error message: "[Application_Name] has been revoked by Microsoft. Please uninstall it."
As a matter of fact, it's said that unlocking the device after should work again and will again allows running homebrewed applications.
Cheers ~ Arne