Book Module 404 Error

I'm running with D6.2 and the latest activemenu. When I enable activemenu and click on the + next to an unexpanded book in a book block, I get this error:

An HTTP error 404 occured.
/drupal/?q=activemenu/book

If I click on the name of the book then it expands in the block. After this first click then the menu will work ok. So I suspect that nodes are not getting initalized properly.

The main navigation and administration blocks seem to work ok.

Here's some specifics on my system:
Drupal 6.2
MySQL 5.5.x
ActiveMenu 6.x-1.x-dev
Javascript Tools 6.x-1.0
jQuery Tools 6.x-1.3

Any help would be great.

beren