I'm afraid I confirm the grub bug. In x86_64 images grub isn't installed to the MBR of the chosen disk (when the boot partition is an extX, if it is reiserfs it works perfectly).

I've tried both grub images (archlinux-2009.01-beta3-ftp-x86_64.iso 30.01.09 12:27 and archlinux-2009.01-beta3-core-x86_64.iso 30.01.09 12:25). I don't know if it would work using the isolinux-based images, if needed I can try those too.

By the way, I forgot to mention the hardware used in testings:

A laptop: 160 GB Seagate SATA, Core 2 Duo 7300, nVidia G-Force 8600GT, all mounted in an Intel motherboard.
A desktop: I don't have it where I am right now, but it was a AMD powered microprocessor, an ATI graphic card, 320 GB HD and Asus motherboard with VIA chipset inside.

All the tests took place in both machines but the x86_64 ones, that took place only in the laptop.

--
Alexander.