Dear Kathryn and other wp engineers.
OK, what happens seems a little arbitrary. In FF18 I find various posts that I can view in Visual, simply by clicking "Edit This", and others that I cannot. Don't seem to see a pattern. For example, it doesn't have to do with the relative age of a post, or whether there's an autosave version of the post, or not, according to the red-font note at the top of the dashboard page).
I have tried disabling all add-ons in FF.
It's very kind of you to take time looking at this anomaly. I'm going to list exhaustively the steps I took to test the way my blog is misbehaving under various conditions (and browsers). Sorry to be boring.
How issues arise in editing:
I. Firefox: Log-in as admin. Go through dashboard to list of posts.
1. First item in list is "Draft post to check link function". I click on the title in that dashboard list (not "Edit). Post opens for editing and i am able to see it and edit successfully. I press "Update" and then "Preview" and everything is fine.
I leave the Dashboard (still logged-in) and view the post as it appears on the blog (not preview). Click "Edit this" in the dateline, and it opens successfully. Edit it, and update, no problem.
2. Second item in list is "Draft to check post disappearing issue". It also works fine both ways (open from list and edit, or click "Edit this" in the dateline, from the blog).
3. Third item in list is "The symphony flashmob videos: Spain and Denmark II". I click the title and it opens to a blank Visual edit screen (i.e., no post content). If I click "Update" at this point, I will create a blank post on the blog.
4. So I click "Back" on the browser (FF18) and click on "Edit" (below the title, in the list of posts) and same result — blank post in the Visual editor.
5. Now, I click "Back" on the browser (FF18) again. Go to the blog and try clicking "Edit This" in the dateline on the blog post (which is still looking OK, because I haven't "Updated" any of the blank pages that came up in Visual editor, above). The post comes up blank in the Visual editor.
6. I go back to the Dashboard list of posts and try the fourth item in the list: "Draft post to test add media button". I click the title in the list and it comes up blank.
7. I repeat step #4 (back on browser, etc.) and have the same result: blank window.
8. I go back to the Dashboard list of posts, and scroll down to choose an earlier revision and I restore it, so I can see some content in the Visual edit window. I press "Publish" and it publishes successfully. I press "Edit this" in the dateline on the post and the screen opens up, Visual edit is working fine.
9. Now, I go up and down in my list of posts (in Dashboard). One after another, if I click on the title of a post that looks perfectly good on my blog, it opens with a blank Visual editor. Same if I click "Edit This" in the dateline on the blog.
This means that any older post I want to revise or update will only be accessible if I go through the steps to choose a revision from the list of past versions and then restore it. And on some of these, the "restored" version is coming up blank as well.
(now I close FF 18 and move on to check in Chrome browser)
Step 10. In Chrome, I repeat step 3 from above, and same result: blank Visual editor window.
11. Repeat step 4 from above, and same result.
12. Repeat step 5 from above, and same result. :(
13. Now, I try accessing older posts either by clicking "Edit This" in the datelines where the post appears correctly on the blog and get the blank Visual edit window.
14. Start grabbing older posts from the Dashboard list of posts and clicking on the title, and each one seems to come up blank.
(now I close Chrome and try same steps in Safari. Same results.)