Mysterious window when switching workspace

[josvanr]

hello

I'm using kubuntu 9.04 and just updated recently to kde 4.3
and have the following issue:
when I switch workspaces (by clicking pager or by using keyboard shortcuts), briefly, a window appears in the center of the screen
(see screenshot), showing the workspace switch, and the dissapears
again. I can't find any way to get rid of this window. Any ideas?
Funny thing is, that when I add a new user (clean home directory)
then the window doesn't appear.....

josvanr

[josvanr]

in case anyone is interested: I found how to switch off this window. In the kde system settings there is a section 'window behaviour' which contains an option 'Popup desktop name on desktop swich'. Turn this off to get rid of the window...