I have checked compilation is disabled, cache is clear, re-indexed, turned on development mode (I get no errors). Disabled MageWorx SEO, set the theme/package to default.
The site will load for example, the account login/register page/ the home page, and a few other pages. However, the site will not load categories/products.
Guessing this is a rewrite issue? Any ideas why this would happen after an upgrade?