The Reverse DNS Lookup Results page has a line:
»There is no need to refresh the page - to see the DNS traversal, to make sure that all DNS servers are reporting the same results, you can Click Here.»
So if I click there, the resulting page has a warning: "For successful result for PTR records use IP address as input" even though obviously I ended up on the Reverse DNS Lookup Results page after having entered an IP address. The "Click Here" probably currently forwards the result of the reverse DNS query which is not an IP address.
Ville