Today, some crazy, unknown contact sent me a message.
From then WhatsUp froze and cannot be used.
I had the same message in N9 whatsUp client but managed to delete it. Here, now in SFOS I cannot and will stay there bugging me.
Tried to Uninstall and reinstall, but all the messages are still there.
Tried to open offline and deleted and muted the group and message, but no luck!
What to delete in order the app to be functional again. Don't care if I have to delete all messages and start over from point zero.

EDIT: Deleted everything whose name was Whatsup and reinstalled. Everything OK now!