I experienced something similar this morning in trying to ad picture to this
reply post in Driveline.
I went to add the picture through the normal process of dragging the file from my PC download directory into the AM box. It acted like it was working but then the file in the AM files list disappeared immediately and showed no files loaded???
In looking closer at the post, it showed it was in UBB Mode only. When I clicked to change that to both HTML and UBB, the functions worked correctly.
On another note - I just tried to click to "Use Full Editor" to look at the settings in this reply. Instead of opening the "Full Editor Mode", it switch the entire page back to the Main Forum Page.
Much new weirdness going on!!!