Where's the candid camera...
I had rebooted yesterday before writing the note. I rebooted again this afternoon around 3 PM Centrai time and got the HTTP 503 error again - no music. I also confirmed that Pandora was working for my on my computer. After reading the notes above that others have had success today, I tried again just now. Of course, it is working again.
Who knows, maybe it was just me, or maybe somebody kicked something somewhere and it started working again (at least for me).