Taskbar Mouseover Failure?

I really like but am having issues with the taskbar mouseover navigation. After boot I can mouseover any icon in the taskbar and it pops up a smaller version of the window for the task. If I move the cursor into the popup it displays the full window. Mousing away dismisses the window and popup. Clicking on the popup restores the full window. That's great [wish I knew the official nomenclature for this process.] But, over time that function fails and I am unable to get to the windows that are stacked. I mouseover and the popups appear but when I move the mouse over the popup it disappears rather than displaying the fullsize window. I have to reboot to get the function back. Very frustrating. So far I have been unable to determine any particular cause or associate the issue with any particular update/software. It is most problematical with Windows Explorer windows as I often have five or six open at once to deal with processing photographic images in numerous flavors. I tried numerous Google and Win7Forum searches but not knowing what search terms to use I didn't get any useful information. TIA.

I have gone there, several times, and find nothing that would cause this functionality to work for a minute to several hours and then suddenly fail.

Windows really shouldn't allow any application to disable its builtin features invisibly. While I had hoped that this was a problem with a known cause/solution, it may not be and I will have to attend more closely to my sequence of events and try to narrow down the cause. The sad thing is that even if I do figure it out the likelihood of getting a programming change is nil.