web.config save problems

[Kleindahl]

Hi all, i have the stranges problem. I have this website running in a cms that i made myself. In the administration the adminuser can save settings that are writen and saved to the web.config file. And all of this have been working fine .... until now. Now when the user tryes to save changes, the browser prompt the user for login credentials again. Does any of you have any idea why this is? I am pretty sure that i havent made any changes to generate this problem. I am totally lost here ... so hope that you can help? Christian