Resharper 3.1 & Visual Studio 2008 - Missing from Add

I'd love to be able to use Resharper w/ Visual Studio 2008 but am having the following issue:

1. I install v3.1 and when I start up Visual Studio and open a project, all the menu items under the Resharper menu are greyed out.
2. Resharper doesn't show up in the Add-In Manager. The Add-In Manager does seem to be working as I've got a Spell Check add in that shows up just fine.

I've tried uninstalling & resinstalling both Visual Studio 2008 and Resharper but with no luck. Here's my machine configuration:

Vista X64 SP1
Visual Studio 2008 Team System
Resharper 3.1 for VS2008

Please let me know if you need any help tracking this issue down.

Regards,
Nisi