Edit: I was thinking for a while that registering is needed to access Yahoo Siteexplorer, but it is not.
its ok if registration is required as long as they dont charge my favourite tool. life is so much easier with it.
In fact, registering is not needed, it was my lapsus, but I guess something is happening on Yahoo, regarding many other users have all kind of problems with it.
I use Yahoo Site Explorer all the time - as far as I know the best tool for seeing who links to other sites