Two Sites, One Menu

I have a client who has two sites for her one domain name. (She has two separate blogs running on the same site.)

So she’s sharing the theme on both sites. Can you share a menu across two sites? The menu I used (using the new menu feature) displays fine on the primary site/blog, but the secondary blog pages doesn’t contain the menue, despite it using the same header file.

Is there a special snippet of code I need to use so that it shows up across both sites? Or do I need to just duplicate the menu in the 2nd site?

Help? Thanks!