Mobile Messaging Not Working

Hi Team,
I am experiencing the following problems with Mobile Messaging;
1. Unable to send Mobile Messages to contacts via PC or via cell using
Contact quick ref number. Some instances I recieve error ""this message was
not sent because messages can't be sent to this mobile number." Other times
there is no error message but the contact does not recieve their cell
message. Please note that I subscribe to Mobile Messages and the contact who
I message have been using this service for 1+ years without problems.
2. When sending messages to contacts offlline is receive the error message
"This message was not sent because offline instant messaging is temporarily
unavailable. Please try again later."

I have tried both 8.1 beta and 8.1 versions and both problems still exist.
Can you please assist. Thanks.
--
AJ