When emerging kde-3.0.5a on clean machine the ebuild does not provide the files:Xreset, Xsetup and Xstartup in /usr/kde/3/share/config/kdm which results in kde dont start. Copying those files from another machine with kde-3.0.4 fixed the problem.
I've put a fix in kdebase-3.0.5a-r2. It's masked atm, but in a fw minutes I'm going to unmask it as ~. It has several other fixes in it as well, so it may be a little time before I can get them all properly tested to move it to the stable profile (since we're in a freeze).
Clarification: the fix is making the ebuild install the missing files to the kdm config dir, not something else.
That revision is unmasked now.