I'll check your ui out, see if the same happens to my system below medium and let you know the results. It does sound like a heat issue, as Callenn suggested. Corrupt textures usually indicate overheating.
The resizing cursor shape is not displaying (when you want to resize some window in layout mode, the mouse pointer should have resizer shape). IT currently displayed as black box. I don't really know where to look for it. Could you please have a look?