While sitting in the XPages on Bluemix workshop in Böblingen these days I experienced problems with my Bluemix user ID. Once I logged into my Notes client it says that the certificate will expire in several days - ooops!
Usually you just enter the security area of your ID using the client and hit "renew" which will cause a mail to be sent to your local administrator. Of course you cannot do this with the Bluemix ID.
In this case you have to rely on the IBM team: as Brian Gleeson pointed out during the workshop the Bluemix IDs were updated during the past weeks automatically. So my first approach was to download another copy of it from the settings page of the data service - but no luck. I can tell you that even re-installing a brand new service won't fix that problem.
There is only one solution: open one of your databases you have on your Bluemix Domino server (normally you would open just the names.nsf but here you can't). This will be a "real" Notes access to the server using you ID which will then automatically update your certificate in the ID. Again Christian Güdemann, who is also here in Böblingen, brought the right hint.