I finally go a chance to look into this, it has been a problem for me but I just ignored it, until now.
If you have had trouble with your Document Information Panel (DIP) not appearing when you open up word (or any Office document), check the settings on the content type (if it is a content type). There is a Document Information Panel settings link that allows you to select if you want the DIP to always be visible on open, it seems to be turned off by default.
I hope the image gives you some ide of it, looks a bit blurry to me.
