some workspaces became black...but not all!

Hi to everyone. I’m not new to linux, i’ve just made a fresh install of leap on my acer laptop with kde5 DE. I became from many years of fedora+gnome, so i’m not a specialist about kde.

I have installed the proprietary ati drivers and everything work fine, apart the problem of the blank icons in systray for certain application (skype and dropbox for example, but i read about the fixing of this problem for kde 5.5) and a strange thing for workspaces; i use 4 virtual desktop 2x2 row; randomly 3 of this workspaces became black and i can only see the mouse arrow, JUST one workspace remain ok. I don’t know where i can begin for debug this problem (that appen with the opensource drivers too). Can someone help me?

Thanks you guy!

Marco