I have a website with the PageLines theme - http://wordpress.org/themes/pagelines.
I have set up a static page as the front page, and another page as the blog page.
When Simply Exclude is activated, no posts are found on the blog page. When I de-activate it, they come back.
I eventually realised it was Simply Exclude by using the hint in this link, which led me into disabling my plugins one-by-one to find the culprit: