when doing emerge '<dev-java/sun-jdk-1.4' portage suggests downloading j2sdk-1_3_1_05-linux-i586.bin. Sun no longer offers that file. The latest is j2sdk-1_3_1_06-linux-i586.bin. Copying the 1.3.1.05 ebuild to 1.3.1.06 and changing the internals to .06 seems to work just fine.
Fixed, new ebuild commited to the portage tree.