Caching breaks node_load()

I added a story and enabled caching. As long as I'm logged in, everything is ok. When I log out and view the node for the first time (i.e. nothing is cached yet), nothing special happens. But when I hit refresh, Drupal reports an error:
Fatal error: Call to undefined function node_load() in D:\drupal-4.6rc\modules\taxonomy_context\taxonomy_context.module on line 17

This error occurs only, when the content of the node is already cached and not with the administrator account.