Out of desperation I tried this. I had to show "Announcements" in the Left Panel first because I do not have it shown by default. Anyway, it didn't work for me. Still getting the message....... Seems to have worked for me across all machines (desktops, laptops etc.) once I've read the announcements.
Okay this is what I did : I went to the Announcements and read all of them. Then I rebooted, and voila, there are no more "Read-Only" notifications. Kinda suspect that the Announcements might be that "Read-Only" notebook that you cannot edit. Still, whatever the cause, it's still a bug. PLEASE FIX !!