I'm having the same exact issue (except my installation is i386 and my machine is Vaio P VGN-P610).
I've tried every possible thing:
Bios: [enable boot external]
Boot order: [external] [hard drive] [network boot]
Tried 2 different USB drives
Tried 2 different external CD drives
Tried 6 different downloads of both the desktop and netbook remix.
All downloads were checked with MD5SUM.
Ubuntu Desktop 9.10 installs properly in every version and from every source.
Getting reaaaally frustrated.
I'm having the same exact issue (except my installation is i386 and my machine is Vaio P VGN-P610).
I've tried every possible thing:
Bios: [enable boot external]
Boot order: [external] [hard drive] [network boot]
Tried 2 different USB drives
Tried 2 different external CD drives
Tried 6 different downloads of both the desktop and netbook remix.
All downloads were checked with MD5SUM.
Ubuntu Desktop 9.10 installs properly in every version and from every source.
Getting reaaaally frustrated.