If you mean you don't remember any userid and password valid for your document, then you have locked yourself out, and you are not able to access your document.Unfortunately there are no "backdoors" or something like that so you can override the section access and get to your document.
You will have to get back to some previous version of your document.
Thanks for your reply, but there may some loop hole to crack the UserId and password of section access. I am doing some tricks to findout the userid and password and i got success up to some level. U can send me one application to test i want to check myself.