importunate flashing window

[Idome <idome tut by>]

Hi All.

I have a small problem:

1. I open workspace #1 and open (for-example, any application have the same behavior) browser there. In the panel
    in the bottom small window is appear. (See screenshot #1)
2. Then I switch to workspace #2 (using Hot Key) and open there some applicatoins. (See screenshot #2)
3. Then I switch back to workspace #1 where ONLY browser was opened, but here I see fashing window from workspace #2.
    (See screenshot #3).

I'm using 2.18 sid Gnome edition. My panel has options "Never Group Windows".

Does anybody know how to resolve such broblem and what does flashing window mean?

Thanks in advance.

Attachment: 01_workspace-1.png
Description: PNG image

Attachment: 02_switch-to-workspace-2.png
Description: PNG image

Attachment: 03_back-to-workspace-1.png
Description: PNG image