Hi Dave,
Just sharing my experience:
I'm using Ubuntu 14.04.1 LTS 64-bit to flash the default yocto build and also your ubilinux. I don't have problem running it. BTW, I don't even need xfstk when using flashall.sh from download page for yocto build (I need to install xfstk, when running flashall.sh from your ubilinux). I got my Edison the day before, so only play one day with it. It come with old firmware so I update the firmware (try both copying to folder, then "reboot ota", and also the flashall.sh script, both work fine). Then I decided I need debian than plain yocto, so tried ubilinux. flashall.sh barked than I need xfstk, that when I start installing xfstk on my 64-bit ubuntu box. Is there any chance your flashall.sh is older than the one on download page? The download page doesn't said anything about version (request), but the file I use was "edison-image-ww36-14.zip"
(I'm back to the plain yocto build right now, since ubilinux not work with bluetooth yet)
Could you elaborate your problem, when you said no luck with 64-bit ubuntu?