windows 7 - taskbar icon preview (and Alt+Tab icon preview) disappears quickly

OS: Win7 Pro x64
Laptop: Lenovo x240
Dock: Lenovo ThinkPad Basic Dock - Port Replicator
Monitor 1: AOC 21.5", E2243FW (VGA)
Monitor 2: Lenovo 21.5", LS2223 (DVI)

Issue:

When hovering the cursor over any pinned/unpinned icon on my taskbar, the preview icon that pops up is quickly fading away (as quickly as it starts up, seemingly with the reverse animation as when it appears).

While holding Alt and pressing Tab to cycle through open applications, the window of icons will disappear (and if I continue to hold Alt and press Tab again, the window will reappear and will start me back at the first icon).

This problem will "randomly" not happen after rebooting and then will begin happening again.

Attempts to resolve:

• Fully run the Windows and ThinkVantage System Updates


• Removed all unnecessary peripherals (keyboard, external CD drive, ect)


• Changed Visual Effects from "Let Windows choose what's best for my computer" to "Adjust for best performance", as well as Custom (all
  unchecked, and tried solely checking "Save taskbar thumbnail
  previews")


• Used one monitor at a time (tried both monitors separately). Lowered the resolution and refresh rate of each monitor. Removed all external
  monitors.


• Used the laptop completely removed from the dock and external peripherals


• Safemode

Comments:

I have seen some registry tweaks that can extend hover time which, as you can imagine, I'm hoping to steer clear of having to make any changes like this. No other Windows 7 machines I've used have had this issue.

My guess is that an application isn't stealing Window's focus since I'm able to leave the Start menu up for an infinite amount of time without it minimizing.

Edit: I notice the amount of time icon previews stay visible varies - they could last 3 seconds, 5 seconds, 10 second, half a second, ect.

Answer

RESOLVED!!!
I have the same issue, similarly, all suggestions never work... the following is my detailed symptom:
When you move over the application icon on the taskbar (that has application opened), you would expect a preview to appear. In this case, although the preview window appears, it will simply auto-disappear (i.e. closed by itself within a very short period of time, e.g. 1 sec). This behaviour is also evident when you use Alt-Tab.

Very frustrating!

Editing the registry, etc, does not help for me. Setting the aero peek (enable or disable or a mixture of those) also does not help.

My Solution
~~~~~~~~~
After trying different ways, I found out that it was due to the battery charging setting!!! - A ridiculously stupid cause.

I believe this is a bug, but if it is not categorized as such, then I supposed the aero peek might be taking too much battery or whatever that the battery setting was configure to close it.

I am using Lenovo T440s. So all I did was to change it back from "Optimize for battery health" to "Always full charge (Start when below 96%; stop at 100%)".

Hope this helps those who find the other solutions not working.

GL-ATB.

Regards, Jacky
[BTW, my original sharing post is here (Taskbar aeropeek preview and Alt-Tab auto close on Windows 7), told to answer directly here instead.]