The download links for the UT2004 ECE do not work (due to server availability I'm sure). Here's a new mirror to hold over. It works right at the command: http://0day.icculus.org/ut2004/ut2004-ECEBonusPack.tar.bz2 I'd suggest a revision on the ECE ebuild and/or send the file to upstream. Opening up the file to being able to unpack the .exe may help as well and open up more mirrors.
Technically, this should be INVALID, as you never bothered trying the ~arch versions of the packages. Remember that soemtimes bugs are fixed in the ~arch versions and aren't back-ported to stable, since we have a waiting period for things to hit stable to ensure there are no futher bugs. At any rate, I marked all of the new ut2004 stuff stable this morning, so this bug will no longer occur with the latest stable packages as of this morning.