maddawg - 2:20 pm on Apr 20, 2012 (gmt 0)
Suggy, A clear OOP is where you fall back from top 5 or page 1 rankings to page 3 or lower for basically all of your keywords.
It's still possible what you're describing is over-optimization(though I wouldn't call it a penalty), and you can tell if that's the case when your site never moves up even when you get high quality links with keyword-rich anchor text. Or if you get links and it moves up a few spots and always falls back to the original position quickly (3 or 4 days).
Keep in mind this test may not be applicable anymore with Google's recent changes to how it views anchor text, but that's how I used to know one of my sites was over-optimized in the past.