WordPress 2.8 Bug
For those of you who have upgraded your blog to version 2.8 of WordPress, which was released last week, there is a bug that is being reported in the forums. The visual editor WYSIWYG menu is lost. Users are reporting this problem in Firefox 3 and in IE8. I have experienced the problem in Firefox only. The best fix that has worked for me is to clear your cache.
Fix – Clear your cache
In Firefox, go to Tools – Clear Private Data, and check the box for “Cache”.