Problem with WLM contacts scrolling

Hi while using windows live mail If I am trying to send a new email to one of my contacts and try to  scroll down the list of contacts having clicked on the "to"

 the list displayed will not scroll properly IE I scroll down move to highlight a contact and it immediately jumps back to the top of the list .

any ideas how to stop this ? 

Its driving me potty 

Thanks in advance for any help offered 

Mike