Many site issues can be caused by corrupt cookies or cache. In order to try to fix these problems, the first step is to clear both cookies and the cache. Note: This will temporarily log you out of all sites you're logged in to. To clear cache and cookies do the following:

1. Go to Firefox > History > Clear recent history or (if no Firefox button is shown) go to Tools > Clear recent history.
2. Under "Time range to clear", select "Everything".
3. Now, click the arrow next to Details to toggle the Details list active.
4. From the details list, check Cache and Cookies and uncheck everything else.
5. Now click the Clear now button.

Further information can be found in the Clear your cache, history and other personal information in Firefox article.

Did this fix your problems? Please report back soon.

Thank you, but...

Didn't accomplish anything.

When I re-logged in to iCloud.com, (which I had to after clearing cookies and cache) I got a message (which I remember getting last time I logged in but had forgotten) saying, in essence That Firefox was not fully supported -- some things might not work properly. And the message (of course!) said to use Safari.

So I guess the inability to upload unzipped Pages documents is one of those "not fully supported" items.

I can live with that.

This cannot be fixed.
Apple is trying to use methods like this, to get people to use their products.

Sorry.
We hope that you will continue to browse with us here at Mozilla Firefox.