Calendar and Mail app invisible in Start Menu

[Impenneteri]

I am encountering a strange problem and I don't know what is causing it. When I turn on my pc, the calendar and mail app is visible and pinned in the start menu. I opened Mail app, started using my PC. After a while clicked start menu to open an application and I noticed the calendar and mail app is gone. So I searched both apps and tried to pin it back to the start menu but when I right click, the only option I have is "Unpin from Start" which means it is there but invisible and there pinned location in the Start Menu is blank and there's nothing to click on.

Anyone encountered this problem?

 

[IainCZ]

Yes, I have the same problem on my Lenovo G580, the app just went invisible one day and I can't get it to reappear. After a short while it just stopped working as well. Very, very strange.