On Friday 26th, BBM was updated for BlackBerry, iOS and Android. A lot of people ran into issues with the update and today we see an update pushed out to fix those issues. If you have been having some problems with BBM since the update, it would be wise to update to this latest version.
It should also be noted that the update seems to reset BBM groups. My past experience has taught me to let BBM settle for a bit and the groups should fully restore on their own. The update seems to also reset your BBM settings, such as notifications.
If you don't see the update yet, try using the link below or carry out a manual search for BBM in BlackBerry World.