From what I hear, the new reddit layout is a resource hog, so it might have something to do with that. Personally I use the
$1 which you can make the default in your account preferences.
To browse posts in the old layout you need to position the cursor in the Jump to Content link, which is the first element in every reddit page, and then press tab to jump to the first and subsequent posts or shift+tab to jump to the previous post. Positioning the cursor in the first element of a page can be accomplished by pressing Control+Home.