Since installing the node access module I see this message randomly. "Content access permissions need to be rebuilt. " Will rebuilding them remove all the node access permissions already set? What does "rebuilding" do? Why do I get this message?
There's a quote in the comments on this post that puts it nicely:
Drupal maintains a table of who can access what; this needs to be rebuilt when a new module affecting user access is enabled.
Think of it as a cache-clear for node access data, except that it's quite complicated so needs to be run as a batch job rather than all at once (e.g. on a cron run).
Since node access is a sensitive issue it's also not wise to rely on scheduled jobs to make the necessary changes, hence why this is all done in one go.
I also was getting this error, after installing the Book Access module in Drupal 6. It turns out I hadn't created any books yet, so that after I had clicked the check box to enable the new installed module, drupal was unable to find found any book permissions with which to initialise the new database table that Book Access uses.
I was able to get rid of the error by
- disabling Book Access
- creating a book page
- no need for content, but do include at least a title
- remember to select "new book" from the dropdown box in the "Book Outline" section of the "edit" tab
- enabling Book Access again
Your situation may be similar.