I got the same issue. The problem is the SMB deactivation in Lion.
What you can do is use finder to connect manually to the BM5. Type:
- cmd+K (or go Finder -> Go - Connect to server)
- in the dialog type smb://<ip number of your BM5>
After connecting, a prompt to enter a username and password will be displayed. Enter these and there it is... the directory structure of your BM5 in a finder window.
In the BeoConnect application you will than see the BM5 as well. At it, click once on it and enter the password and it will work again.