This is a common problem for many folks around the Internet. You do some sort of an upgrade in WordPress, and you lose your “Visual” tab in the editing page, or you lose your buttons, etc.; all you have left is the “HTML” editing option.
This seems to happen to me every once in a while when I do upgrades, too. And it happened to me again today, while upgrading to 3.3.1.
And, like you, I do the fresh replacement of wp-admin and wp-includes, and it doesn’t do any good. I check the error logs. I check other browsers and versions. I clear caches. I do a few other things that I find in the WordPress blogs. All to no avail.
Well, I’m here to remind you AND MYSELF that next time this happen, just restart Apache first (of course this might only apply to those that have the luxury of a self-hosted site). If that doesn’t work, (and it probably will), *then* do all those other things.
😉