Ok I see.... The dingbats over at DNN Corp have decided to move browser inputs like checkboxes and radio buttons behind the page in DNN 7, just so they could overlay them with their own graphics. They've done it by auto-injecting inline styles. It's unbelievably inappropriate. I've already complained about this to them, but that was obviously a waste of breath.
I'll need to sort out something when I get onto DNN &, but for now you can try something like this:
input {z-index:0 !important;visibility:visible !important}
It'll need more than that to fix it, but that should bring the inputs back to the fore.
Regards
Rob