Skeeter Rae

Is it possible for someone to see your IM's? Can they hack your account and see your conversation history? Or get in to your harddrive through SL? the other day my IM would be sent but what I typed would stay in the queue, I would need to delete the message before I could type another or I would send the same message twice. The person I suspect, the message they were sending to me would be sent twice. Am i paranoid or should I be concerned?