Missing tool icons in Blogger

In the Edit HTML mode, the toolbar in the Blogger Edit page has 7 tool icons. However, in the last 10 days or so, the first four of these went missing on me. It didn't matter which computer I used or what blog I was trying to edit, these tool icons just wouldn't appear.
However, it only happened in Opera. Firefox and Chromium were unaffected.
The Blogger Tips & Tricks blog mentions this problem and he apparently is able to solve it just by opening another browser.
Well, that didn't work for me so I used to write my stuff in Opera and insert the links and quotes using either Firefox or Chromium.
Today, after 10 days without a break these tools came back. I really cannot explain this but it's nice they're back.
But I wonder how long before they disappear again equally mysteriously.