Have you tried to click it anyway?
I have a similar issue after I factory reset my device. App shows installed already, but when you click on "Installed" button you can download it again.
Yes clicking on it on the phone gives an error, "The download of BeyondPod Unlock Key was declined because you haven't purchased it.", and when I click on install in my browser on my pc it says "This app will be downloaded to your device shortly." but never gets sent. Also I would like to reiterate that I do not own this app, it was once installed as a cracked app, but I have since deleted it to purchase the sale item from the Android Market. But I can not because it shows as purchased and will not let me install because it is not purchased. I have no way of purchasing the app.
This is just one instance of this as all my cracked apps and apps from the Amazon App store show up as purchased in my Android Marketplace.