I have a rather strange problem with Windows 7 (64b) on my Lenovo Thinkpad X121e.
When the cursor goes outside the active window after a second or so the window over which the cursor hoovers becomes active and is put in front of all other windows even though no button was pressed in this process.
When I open a window (not maximized, just normal) from the taskbar I have approx. one second to rush to it or the window I just opened disappears and the window over which the cursor is in this moment becomes active and in front of all the others.
This problem is very annoying especially when there is one window maximised and few other (normal size) in front of it. Then all the smaller windows disappear when the cursor gets for one second over the big window
The problem does not go away even when I update to most recent Lenovo drivers. The problem was present even before I installed the Logitech wireless mouse, so the mouse is not the problem.
Try the following configuration change:
1) Open control Panel
2) Select Ease of Access
3) Select How the Mouse works
4) Uncheck (if checked) the box "activate a window by hovering over it with the mouse"
You can also reach this control box by searching in Control Panel for "window arrangement". Follow the "turn off automatic window arrangement" link and make sure "Activate a window by hovering over it with the mouse" is not checked.
This setting may be causing the described symptoms.