Did it ever crossed your mind that the router is broken?
I mean like a hardware malfunction.
I'm sorry to say this but if you're unable to access the router even with use of a cable then I think there's nothing left.
I hope I'm wrong but I'm afraid I'm not.
What I would try is to pull out the plug and leave it for a night. (you never know and you don't have anything to lose.)
theoreticly that wouldn't solve at thing but sometime technology is a strange thing.
You might want to check the book if there is any way who you can total reset that thing.
Sometimes there is a tiny hole in the back of the router.
(Sometimes its marked with reset sometimes it isn't.)
Jonas