EDIT: The problem seems to have sorted itself out. Not sure what caused it but seems to be fine now.
I've just upgraded from 16 to 17 and everything has gone fine as far as I can see except one point.
From 16 the upgrade has preserved my 4 workspaces and two panels with all their bells and whistles. However my background is just black (the splash screen shows the Beefy Miracle fireworks, until my workspaces load) and the widgets I had on the background have disappeared.
I would normally just reconfigure my backgrounds as I wished, but what is weird is that I have the 'fade' transition when switching and, for the duration of the fade, it displays my old workspace, with the Verne background and my CPU/RAM/Network monitoring widget, as well as some icons (trash, terminal, home folder) that I didn't have. This is a bit annoying as it flashes up a completely different layout whenever I switch.
Is there anyway I can make it forget this background it's showing during fade, or better still, get my old setting back?
I'm on KDE 4.9.5 if that makes any bearing.
If you need more info please let me know.