VePro7 added support for AU3 with multi midi ports in a much better way. So much better. Highly recommend you upgrade.
You'll have to describe in more exact details what you have done and having a problem and/or post the LPX project you're having a problem with, in order to help you. make things work right. It works, but since its not working for you, then it depends on what you did to get where you are.