Comment 162 for bug 709461

If you are still interested in this bug I have an almost guaranteed way to reproduce it. But it's slightly demanding of your work environment, since it means using MATE desktop environment and replacing it's WM 'marco' with 'compiz'.

Once you have this Compiz/Mate combo running, you need to open a few windows (I typically have >10 various applications open so this bug hits me often).

If you minimize al windows, using for example panel Show Desktop Button or a keyboard shortcut defined in CCSM (I have Super+M setup to minimize all windows) you will almost certainly create one of those "ghost" windows that are clickable and block access to desktop icons and sometimes even windows below them, but are invisible.

If you want the nasty version of the bug (where a window even disappears from taskbar so you cannot remove it any way but sucessfully guessing where it's close button is located) try tampering with CCSM options Enable Widget Layer.

Minimizing by clicking the taskbar button instead of window's minimize also hels bring this vermin to show it's face.