Does anyone know what would cause this error? Everything was working fine and one day I restarted the Web Proxy service and I got this error, but I had restarted the service several times after the last changes that I made without getting this error. Disk cache D:\urlcache\Dir1 failed to initialize. Invalid volume specified. The volume must be a NTFS volume with supported sector sizes. Specify a valid volume as a cache drive. You may need to change your hardware if the required sector size is not supported. Restart the Web Proxy service. Identify the reason for cache failure by examining previous recorded events, or the error code. The error code in the Data area of the event properties indicates the cause of the failure (internal code: 504.1277.3.0.1200.50).