Sorry for the late response. :/
@Deadly Delta - We haven't yet tested Viber on Xperia X8. Since the Android OS covers a large array of devices we are working around the clock on testing Viber on different devices. We appreciate your feedback and will definitely look into this matter. We are about to release a new, more stable version in few weeks and would be happy to know if it has resolved your issue. Thank you!
@newtoandroid - You might want to check this thread in order to get some answers: http://www.boards.ie/vbulletin/showt...did=2056398786
@Sneachta - This feature is highly requested and it's being discussed at the moment for future releases.
Meanwhile, note that when you make a Viber call, if it says "Ringing..", it means the other side's phone is literally ringing, meaning they're online. If it only says "Calling..", it probably means they're offline.
Same for messaging - if you send a text and you see the "✔" sign, it means the message has been received at the other side's phone (he's online). If you only see the arrow sign, it means it's been sent from you, but pending the other side to come online (they're offline at the moment).
Think of Viber as a "substitute" to your real phone. When you call/text someone, you're not sure if they are currently available or not. Right?