Hello Mt.Gox Users,
It appears that trading is currently unavailable and open orders cannot be cancelled. We are investigating and working to resolve this issue. Our apologies for the inconvenience caused and thank you for your kind understanding in this matter. We will post an update to this problem once we are able to resolve this.
Resolved: Trading has resumed and open orders can now be cancelled. Once again we apologize for the inconvenienc caused and we appreciate your patience while we have been working to resolve this matter.