Just tried a fresh install of @kde 4.5.1. When it got to kget, it failed to compile complaining about missing powermanager.h (which is provided by solid). Sure enough, solid had not yet been installed. After installing solid manually, kget (and the rest of @kde) finished compiling just fine.
Have you tried 'emerge solid'? If not I recommend trying that.
err, I just saw you tried that. never mind me.
Indeed, deps needed to be revisited. Thanks for head up.