circumstances :-) annoyed, but relieved now. System: Windows 8 PRO 64, fine hardware and latest software. Intelligence: sufficient. Stamina: way to much...

In the Desktop mode, the mouse has a erratic behaviour when popping up icons in, amongst others, the SysTray, Start menu, Skype Emoticons and so on.
When I click on the respective part (ie. stary menu) and move my pointer up to display the list of items, the items -disappear- instantly. This makes it practically impossible to select any of the items.

Go to the function in Ease of Access (control panel) "change how your mouse works", "activate a windows by hovering over it with the mouse". This should be DISABLED (unchecked).
All works fine from then on.

Have a good one!