Here's a mystery for you. I created a Custom Post Type called "portfolio". Then I wanted a page template to show just those CPT's. It's a custom loop with paging, and it works perfectly if I don't call the page "portfolio" (that is, the permalink) - if I use that, it shows my static home page instead, no loop output. Very odd, since the page I'm using is not the front page.
My first thought is that maybe by using a permalink that matches the CPT name, I'm running into some standard core loop or something.
Or maybe I should just use an archive template instead of using a page template? I was considering the page template so I could have some custom output on the first page, maybe via a custom field.
I am using a cache, but I tried clearing the cache and even disabling it. Same thing.
My permalink structure is /%post-name%/