I believe I may have found the culprit. I just checked to see if the problem was back yet (it wasn't) but then I noticed when I hovered over the 'Search Magnifier' next to the Start button a recent searches menu appeared (see screenshot below).

This menu immediately went away when I moved my mouse cursor but then I noticed the busy cursor was back again. Right clicking on the Search Magnifier causes the magnifier icon to turn blue, it stays that colour until I moved my mouse beyond the active area shown in the red box below. Moving past that area made the magnifier icon turn white again suggesting that the icon only remains blue and active whilst I'm hovering over the search menu. Incidentally this 'Search Menu' pop-up doesn't always appear which also suggests that it might still be active when the user cannot see the menu, hence the problem we are all experiencing.
Update 1
I've been playing around with this a bit and notice that I can move this invisible active area by choosing too show the start menu on the left of the screen. This seems to confirm my theory, this active area seems to follow the 'Search Magnifier' recent searches menu. Ironically however, removing the search magnifier from the task bar does not remove this problem.
Update 2 - Temporary Solution/Fix
So I have found a workable solution, ..in the interim at least. When this issue arises, Right Click the Start Button and open the Task Manager, then on the Processes Tab scroll down and find 'Windows Explorer' (Yellow folder icon) and then 'Restart' the process. This will cure the problem temporarily until it happens again. As I suspected this issue is caused by the 'Search Magnifier' - 'Recent Searches' pop-up menu.., after restarting Explorer.exe just now the recent searches menu is now working again, it wasn't working while the cursor was showing as busy.
Things that I have noticed can trigger this busy cursor issue:-
- Hovering the mouse over the Search Magnifier in the Task Bar
- Pressing Windows Key+Print Screen on Keyboard
