Hi,
This is a member of Viber's development team.
We are aware of some issues with OS 4 and presently our Android development team is hard at work concerning these issues. We will have a solution for you within the near future.
Thanks again for your support and your patience.
Viber Team
Unfortunately there's no Beta
But - we're doing our best to solve this as soon as we can. Viber 2.1.3, that should already support ICS, should be released within the next few weeks.
We apologize for the temporary inconvenience.
Very interested in a fix as well. Glad the development team of viber is responding and working on a fix.