When I click on Edit for any of my posts, I get an empty box; the post to be edited is missing. I try clicking on the HTML button and there is nothing there also. I have not been active in the forums for a while and this has been happening to me for a couple of months at least. At first I assumed it would be fixed, but the problem persists for me and is consistent; it always happens for me. I tried looking at the past couple of month's threads here (in this forum) but I don't see anything describing this problem.
I will try deleteing the Microsoft cookies.
Update: Just to be mischevious, the forum software is working for this thread. I am adding this test using the Edit button.
Another symptom is that the post to be edited does appear for a fraction of a second, then disappears.