As we communicated earlier this year, the New Google Drive will soon become the default experience for all users and the prior version of Google Drive will be retired. NOTE: the new Drive UI does not work with older unsupported browsers and users need to be on the newer web browser versions to access Google Drive. See Supported Browsers for more information on the Google Apps supported browsers. To avoid any issues, users should upgrade their browsers by June 23, 2015. MiWorkspace users should not experience any issues as their web browsers are automatically upgraded.
For more information, see An Update on the new Google Drive UI.