When dragging clip within timeline, no outline shows, only time-stamp
When I click on and drag a clip within the timeline, normally it shows an outline of the clip, allowing me to see where the clip will end up. Now, when I click and drag, there is no outline, it only shows a timecode increasing or decreasing as a drag left or right.

(Pictured is me dragging the clip with no 'ghost' clip overlay to indicate where the clip is going)
Have I hit a short-cut key by accident, or is this a bug in 15.1? I've reinstalled 15.0 and the problem goes away. All drivers are up to date.
I have tried searching for a solution but all results are regarding dragging a clip INTO the timeline. My problem is dragging once in the timeline.
In addition to this, none of the sub-menus display in my Tools panel, and when I click a top-menu item for the drop-down, none of the sub-menus appear when rolling over a menu item. I have to click the menu item for the sub-menu to appear.
TIA
