Windows Task Bar Item flashes when I click on it rather than opening

• Try right-clicking the program on the taskbar to see what options are provided in its menu; it might be that an option besides "Open" is default, such as acknowledging a new message, etc.
• It might be that the window for the program is open, but not visible, due to multiple monitors or a glitch in the program's settings. One way to fix this is to shift + right-click on the taskbar button, select "Move" and then tap an arrow key on your keyboard to lock the mouse cursor to the window. Finally, move your mouse cursor and the program window should snap into visible monitor real estate.
• Some programs have options to show in the Notification Area (by the clock, once called the system tray), or as taskbar programs or both (for example, WinAmp). You might want to look at your program settings to see if it offers this option. In some cases, double-clicking the notification area icon brings the window back, but single- or double-clicking the taskbar button seems to do nothing.

It happened to me also after one of the notification pop-up got frozen. Try to start Task Manager, go to processes and kill explorer.exe, and go back to the first tab "Applications" and press "New Task..." button and type "explorer.exe" and press "OK" button. Hopefully new instance of the explorer will rectify Areo bug.