There seems to be lots of problems this morning too:

www.hilton.com and www.hhonors.com both produce the following error:

The page isn't redirecting properly

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

Earlier this morning I tried and got a garbage page instead.

iPhone mobile apps aren't working either.

So something in Hilton's IT dept has gone very bad. Either that or they are the victim of some kind of hacking attacking.