ALT+TAB does not workings for switching applications

I am facing a bit weird issue on my system. I am using Windows and I am no longer able to use Alt + Tab to switch applications. When press that keys I can see the Windows switch screen. But when I release the keys that did not worked all. It looks that Windows is not responding when I try to choose a new window. The issue is a bit weird which is really uncommon. Here are some of things that can provide more highlight :

1. First the keyboard is working quiet fine. There is no issue with the ALT and TAB key. They are not getting stucked. I had checked that in Word by testing a different number of things. I have a USB keyboard with me and it is just purchased last month.
2. Another thing that proved my keyboard works fine is through Remote Desktop. I connected to another computer in Teamviewer. When I press Atl + Tab in that it worked. I can change the windows.
3. I had tested one more thing. I had created a new user account in Windows. But still the same problem.
4. After restarting computing in Safe Mode the keyboard starts working fine.
5. From Task Manager I had killed the process explorer.exe. I had kept cmd, and Explorer working on the backside. At that point when I press Alt + Tab the same did not worked. So does this issue lies with Windows shell.
6. Now this thing has confused me more. When I hold both the ALT key (left and right) for sometime and then release it and again when I press the TAb key I can switch the apps back again. But it does not work when I use the left alt + tab sequence.
7. I am not sure that this will be associated with the hardware that I have. But the problem appear when I added a new Nvidia 6600 graphic card in my computer. I had installed some accounting software and games after that. I had updated my gpu's driver and also checked it was working fine. To ensure that this is not a gpu issue I re-installed the card a number of time.

You can fix that issue by changing Windows Theme a couple of time. There can be some service which fails to start and cause this issue. This is simple to do. Just follow the below steps.

1. First right click on the empty area of desktop and click on Personalize. You can also access the same from Control Panel.
2. Now click on Theme section and choose Windows Classic. Give OK. Your Windows theme will be turned to basic look.
3. Check that Alt + Tab in working in this or not. If yes then again follow the same above steps and change your theme back to original.

It looks you will have to go through this process again and again making it a bit complicated to use. I am looking for a more intact way to fix this out completely.

The problem lies with Windows shell. It can only be fixed by rebooting. There can be certain files which are not able to load properly on start and cause the issue. You must reboot now and then simply check back. Try to log off and login. This will work I think.

I've got a very similar problem that isn't solved by changing themes.

Any ideas?

Thanks for posting this solution! I used it just now and wanted to let you know that this solution also works for Windows 7.