Updated to WP 2.8 last night with no apparent problem. Everything was where it should be and all the plugins worked.
Early this afternoon, the instant updater plugin and TinyMCE Comments plugin both updated. That's when the trouble started.
In Firefox 3.0.11, the form frame for comments is only visible for a fraction of a second when the page first draws. TinyMCE's editing tools are nowhere to be found. The following text string appears within the comment form, but only for a fraction of a second:
In Internet Explorer 7, the TinyMCE comments form frame renders OK, but that spurious text string is there.
It is possible to enter a comment, although few if any visitors would know where and how without seeing the form to work in. So, I have deactivated TinyMCE Comments. I left a message at the plugin author's Web site, but noticed a request there to mention any problems with the update here.
I tried deactivating Spam Karma 2, the Ajax Comments plugin and several other things, one by one, to see if doing so would resolve the problem. Nothing at my end changes or resolves the problem.
I hope someone here or the TinyMCE Comments author will be able to fix the plugin.