What a pain...
I finally figured out the problem I had with the wysiwyg editor not always showing up. It was driving me crazy, sometimes working, sometimes not.

I thought it was the browser (IE v FF). Maybe it was different templates, or a CSS error. Uploaded newer versions of different editors (JCE, JoomlaFCK) Finally found out it was HOW I was accessing the admin area.

If the site is set to use the www (as in www.domain.com), then you MUST access the admin area the same way.

Example. If you set the site to be 'live' with www.domain.com, when you or a visitor gets to your site, if they typed in or followed a link for simply 'domain.com', your site will come up and automatically shift to www.domain.com. If you then login and follow the admin links to login to admin area, you will always be in the 'realm' of www.domain.com and all should work fine. If, however, you go directly to the admin section, ignoring the www (ie. domain.com/administrator/ ) and login, your 'session' started without the www and you may end up with errors, especially with those editors.

Much wasted time on this one. Hopefully a thing of the past now.

seems to be a thing of the past with joomla 1.5, but always good to watch for.