I don't see that your explanation covers both conditions. Apparently your saying I have permissions to view the page.

Ok, so I can type the URL directly into the browser and the page displays. So, I have permissions to view the page.

I open my word doc, and I still have permissions to view the page. I click the link in the word doc that goes to the exact same url, and I still have permissions. Yet - I get the error and I can not view the page.

What happened to my permissions ?