Deleting the locked file will help. For example, if you are facing problem with the page "http://www.yoursite.com/mypage.html", then in the Contribute browse to the lock file of the page "http://www.yoursite.com/mypage.html.lck", then choose File--> Actions--> Delete Page. This will delete the lock file of the page and you can edit the page.
Now you can easily manage locked file using Adobe Contribute 6.5. More on http://blogs.adobe.com/contribute/2012/08/adobe-unveils-contribute-6-5-with-html5-support. html