Thanks foor adding unetbootin to portage btw. USB key is unbootable because unetbootin creates 0-length vesamenu.c32 on USB key because it opens /usr/lib/syslinux/* instead of /usr/share/syslinux/* I guess files were moved in some recent syslinux update. I am using an up-to-date vanilla ~amd64 but syslinux's files are located at the same place on my ~x86 box, both using syslinux-3.72
Created attachment 177968 [details, diff] /usr/portage/sys-boot/unetbootin/files/unetbootin-304-cpsyslinux.patch Simple patch that tests whether files exist under /usr/share/ and uses upstream default when not. Tested on vanilla up-to-date ~amd64 box, generated key from jaunty-alpha2 for x86 and booted my eee fine, if you must know :)
Thanks. I applied the patch in -r1. Maybe I should send this upstream, but I am treating it as a Gentoo oddity for now.