I upgraded to Slackware -Current earlier after a fresh install of 13.1, bringing KDE up to version I'm using KDE 4.5.5. I logged in with my User account, configured stuff, installed stuff, the usual. I even logged out and rebooted a few times. Everything worked as expected. I logged into XFCE for a few hours while I transfered files (for some reason Dolphin wasn't reading the folder sizes correctly and wasn't transferring everything, I had no such problems in XFCE). When I logged back into KDE I found that desktop effects weren't active, even the work spaces on the left were arranged in a line rather than two by two. Also, Akonadi server doesn't start up when I log in anymore.

In Desktop Effects settings I am told that they are not available, though I am given no reasons why. I tried to restart them and got some error message about how another program was stopping them, and I could use a keyboard shortcut to activate them. I did so but nothing really happened. After a couple of restarts I no longer get that error and I do have basic effects like transparent panels and windows become transparent when I move them, but my All Effects tab is empty. For the sake of experimentation I logged in as root and everything was as it should be; Akonadi started up, workspaces were arranged two by two, my all effects tab was full and I could use any effect that I wanted... I'm not sure what is going on, I have very limited KDE experience, so any help would be appreciated.

Try removing ~/.kde4/share/config/kwinrc