posts and category pages not showing

Hi

I upgraded to the latest wp, though I think this problem actually started with the previous upgrade, I just didn’t notice it (I did see it on another domain but I had moved it and assumed it was a problem associated with that).

Anyway, when I click on the links to my categories or posts, it comes up in my browser that the page doesn’t exist. But when I look for all my previous posts, they are in the database and I can see them from admin.

I’ve disabled all my plugins, and the problem still persists.

Any help would be appreciated.

Thanks
Rebecca