This is a common thing with BBM. I have had 5 BB's now and every one of them has had some sort of tweeky issue with BBM. I would like to see someone develope a messenger like JiveTalk that includes BBM. Then maybe these issues will be resoloved. I don't think the team at RIM spends a lot of time playing with the messenger feature!!
Once you go Black(berry) you'll never go back!!!