During maximizing CKEditor sets the html and body elements' size to (0,0). Looks like opacity in FF doesn't really like it... Perhaps you should fill a bug report on this issue.
Certainly you should file a bug because your testcase is quite simple so it can be properly investigated to find out what's the problem. (just follow the link in my signature)
Re: 'Maximize' makes website disappear with Opacity (FF4)
During maximizing CKEditor sets the html and body elements' size to (0,0). Looks like opacity in FF doesn't really like it... Perhaps you should fill a bug report on this issue.
Re: 'Maximize' makes website disappear with Opacity (FF4)
Re: 'Maximize' makes website disappear with Opacity (FF4)