So I found this post here and have now exactly the same issue.
I did the diagnosis as written in above linked post and this is the result:
The images are too big for here so this link must suffice: http://imgur.com/a/UfBfc#0
Next step for me, as 24" Monitors do not get a Service Tag would be to call Customer Support next thing tomorrow (as it is too late for that now). Or is there anything I could do else?
Thanks!