I thought this was a common Windows bug, but since the search terms were so common, it was very difficult to find a discussion on the matter online. I had a frequent problem where an application would bring up a modal dialog that would get very easily trapped behind the parent window. That is, a dialog box would have focus that could not be shifted to the window that spawned it, but the dialog box itself would not come to the forefront so it would be obscured. Trying to switch using the taskbar or alt-tab didn't usually help. Regrettably, I thought the problem was due to bad programming of the applications that demonstrated the behavior, like Iolo System Mechanic 8. It turns out the problem was instead due to a software conflict...
Quitting Acer GridVista and stopping it from running at startup fixed the problem. Similar stay-on-top shell enhancements might interfere also.
