Hello, calster:
Word 2010 64-bit cannot run plugins from 32-bit programs like Reference Manager. For this reason, Microsoft suggests that most users install Word as the 32-bit installation, even on a 64-bit OS. See http://office.microsoft.com/en-us/products/microsoft-office-for-home-and-school-faq-FX102926087.aspx#, scroll down to “Should I install the 32-bit or 64-bit version of Office?”
If you wish to run plugins like Mathtype or Reference Manager, you would need to install the 32-bit version of Word 2010. I sincerely apologize for the inconvenience.