Container Access in Windows Azure Storage Resets to Private

Hi
We are new to Windows azure though we have learnt good amount of things and are quite fast learners.
We have used Windows azure storage for blob objects while developing sitefinity application but this storage access resets to private automatically after certain time period (30 mins or so) and then the pages where these images are accessed are stopped displaying.
Please check the file attached to see the screenshot.
Then we have to manually login into windows azure storage and set this to Public Blob or Public Container and then it start displaying.
Please help me to solve this. I think I am missing some settings for this.