Issue:
While working on a client's MOSS 2007 Publishing site, we ran into an issue where we simply couldn't create any CMS pages. After clicking Site Actions -> Create Page, the page would act like it was posting back and, after a several minutes, would either time out, or prompt me for my credentials 3 or 4 times in a row only to finally display a "You are not authorized to view this page" error. The same happened when attempting to create a page from clicking "New" in the Pages library, clicking "Create" on the View All Site Content page then clicking Publishing Page, or clicking New on the Mangage Content and Structure page while in the Pages library.
Probably cause:
This all started happening after I went into Site Settings -> Page Layouts and Site Templates (under the Look and Feel section) and modified which Page Layouts were available for the user to select when creating a new CMS page. Figuring the issue lied in this change of settings, I tried to go back into the Page Layouts and Site Templates settings page again, only to discover it was acting the same way as the Create Page function.
Resolution:
Having no error information to go against and nothing useful coming from the bumped up logs (except an unknown lockfile error which we can't even be sure was linked to our issue), we took a shot in the dark that our issue was permissions related. The user we used to change the Page Layouts and Site Templates settings was a Farm Administrator, Site Collection Administrator, and had Full Control on the particular site we were on, not to mention the fact that we were able to change the Page Layouts and Site Templates settings with this user in the first place. However, we logged in with the System Account and voila!!, we were able to create a CMS page AND access the Page Layouts and Site Templates page.