PowerBI returns 401 errors since 26th of January

We believe there is an issue with the PowerBI REST API currently. Since 2016-01-26T21:56:11.892Z  we see 401 errors appearing, even though the credentials used are valid. 

Example response: 

I2016-01-28T08:15:28.829Z]{"uuid":"724eb3e7-4ca5-42c7-6bca-b02a3fad28fb","status":401,"headers":{"Cache-Control":"no-store,

must-revalidate,

no-cache","Connection":"close","Content-Length":"0","Content-Type":"application/octet-stream","Date":"Thu,

28 Jan 2016 08:15:27

GMT","RequestId":"e2bd3d9a-16dd-40fe-9923-e49906105aad","Server":"Microsoft-HTTPAPI/2.0,Microsoft-HTTPAPI/2.0

Microsoft-HTTPAPI/2.0","Strict-Transport-Security":"max-age=31536000;

includeSubDomains","X-Content-Type-Options":"nosniff","X-Frame-Options":"deny"},"text":"","buffer":[],"cookies":{},"source":"ms-error"}

Does anybody experience the same issue?