I've posted about this before:

Whenever I install KDE and try to run startkde, it complains about the
ownership of /tmp/.ICE-unix; it wants it to be root, it isn't.

The only way around this I've found is to mkdir -p 1777 /tmp/.ICE-unix
as root, e.g. in rc.local.  One could add some logic to /etc/rc.d/kdm
to check for this.

Of course, I'd like to know if there's something peculiar about my
setup that's causing this (aside from perhaps /tmp being on
mfs/cleared upon reboot).  If you look on google, you can see that
many different groups (slackware is one) do what i'm talking about
here.

Unless my setup is hosed (I don't see why it would be, I simply did
'make install'), this issue should at least be mentioned somewhere in
KDE's MESSAGE files.

--Blair