Disappearing taskbar icon highlights.

When portable application is pinned to taskbar and running, after a while this application will lose its taskbar icon highlight, application is still running though because I can see it in my Task Manager, but when I click its taskbar icon it will open a new program instance instead of already running application, it failed to open already running application because taskbar icon lost its highlight, this problem occurs only with portable application, version 4.2.2 didn't have this problem. And this problem occurs with all portable applications which I have tried.

So the problem is: Portable application which is pinned to taskbar will lose its highlight after a while.