recently, possibly since latest update, imessaging fails, have to send messages as sms

Hey Hathibaba,

Thanks for the question. I understand you are experiencing issues with iMessage. The following article may help to resolve your issue:

iOS: Troubleshooting Messages

http://support.apple.com/kb/TS2755

You may also want to reset your network settings:

Settings > General > Reset > Reset Network Settings.

Note: this will delete any network related settings (saved Wi-Fi passwords, etc), it will not erase any content from your device.

Additionally, you may find the steps in the following article helpful if your issue is unresolved:

iOS: Troubleshooting FaceTime and iMessage activation

http://support.apple.com/kb/TS4268

Thanks,

Matt M.