Gox also says quite clearly that their system will not work with SatoshiDice.
Ah, but the the "quite" part is in the eye of the first person that did not see it.
Please be advised, that MtGox only lets you know about this incompatibility if you happen to hover over one of the identical blue help icons on that page.
It's also on satoshidice's page. Once again, do your due diligence beforehand. It's still not GOX's fault. And I hope by now you have set up your own ewallet or desktop wallet somewhere and aren't using gox as your personal wallet right?