Hi folks,
i share the same issue and frustrations with all iPad 2 users here. After reading this post and disabled FaceTime iiPhone Cellular Call, it didint help. I havent enabled iCloud Drive, but thought of checking it out anyway.
One strange thing happen. After I go to Settings > iCloud Drive, the No Service sign will quickly turn to Searching and soon my cellular service is back up and running. This leads me to think our issue is linked to iCloud Drive rather than FaceTime.
The No Searching issue will keep come back, but the work around of going to iCloud Drive to bring back the cellular works for me, rather than having to reboot the iPad everytime it happens. Hope this help other users, and fingers cross 8.1 solves this for us.