[cookdav]

That checkerboard is their default plasma 'zoom-out' pattern, etc.

But, just deleting your .kde4 sub-tree SHOULD put you back to the
initial first-time user (default) layout, so I'm totally mystified why that
didn't work. I'd try it again, tho.

That said, I think I figured out that they may be keeping some piece of initial-context
over under .kde3 subtree (if you have KDE-3 installed, which of course I do).
So, for a test, you could try renaming .kde3 to .kde3-save, delete the .kde4,
and see if that fixes it. Of course, the usual caveat applies...you have to
re-tailor the desktop(s) back to your normal preferences.

Keep us informed how it goes...you got me curious about what's going on
on your machine.

EDIT: One last thought: They probably also keep a 'template' somewhere of
what the inital-setup for a new-user is supposed to look like, so if THAT got
modified, it would explain what's going on. (Don't know where that is off
the top of my head.)