This has been happenning for some time, but I have a few more concrete details.
First, I am using Win XP SP3 with IE8.
Second, I now know that I cannot edit a post for a 3rd time without logging out closing the browser and then finding my way back in again.
Third: When I edit the first time I have no problem; the presentation allows me to place the cursor and edit the text. However the next time I try to edit, I get HTML. I can still place the cursor and delete and add text, but that happens inside the HTML.
The third time, I see HTML and the constructs of the frame and buttions inside the normal frame of the post. I cannot place the cursor; clicking somewhere selects a component - usuallt the frame iof the text insde the normal editing frame. The selection
is a "bolded" frame with handles at the corners and sides. This happens again thereafter. The sequence can be prepoduced reliably, and will not stop until I at least close the browser tab.