Someone correct me if I am wrong, but there is no transaction going on with posting a message to a BB that would get you a virus. Even receiving e-mail, it has only been recently that viruses have crept up that you can get without actually running an executable attachment. And those that you can get only effect the mail system, not the entire computer.
Anyway, I think I can safely say that unless you downloaded something, you didn't get the virus here.