Since the issue exists only in your development environment, a workaround would be to use a browser that implements a 'private' mode such as Google Chrome's incognito mode or Microsoft Internet Explorer 8's InPrivate mode
These browsers, when operating in these 'private' modes do not keep the cookies and temporary internet files after you close the window which should solve your issue.
However, it should be kept in mind that these browsers might not be fully compatible with the website you are developing.
Moreover, you should provide more information regarding the implementation of your website's authentication and your website in general if a more permanent solution is to be reached.