I just tried installing Arch on my macbook pro 7,1 from the 2011.02-2 archboot. I was following instructions on the Macbook page, as well as the Beginners' Guide. Partitioning and installing the core packages seemed to be successful. When I got to the bootloader stage, I was having problems pretty much as described here. The only bootloader/installation point combination that didn't hang/ give errors was loading LILO on /dev/sda. LILO loads, and I can choose between kernels and give boot options. When I try the regular kernel, booting stops with the message, "Unable to determine major/minor number of root device /dev/disk/by-uuid/[uuid]" and then says "/bin/sh: can't access tty: job control turned off" and gives me a [ramfs /]# prompt. However, when I type nothing happens. (The cursor is blinking, so it isn't frozen.) When I try the fallback kernel, I get as far as the regular login prompt, but again, nothing happens when I type.
I've tried the boot options "arch noapic irqpoll acpi=force" suggested in the macbook wiki. This doesn't change anything. My /etc/lilo.conf has the lines:
append="root=/dev/disk/by-uuid/[uuid] rootfstype=ext4 acpi=force"
There is a similar entry with /boot/kernel26-fallback.img instead.
In mkinitcpio.conf I have loaded MODULES="ahci libahci ehci-hcd ohci=hcd ext4 vfat" and HOOKS="base udev autodetect pata scsi sata keyboard usbinput filesystems". In rc.conf I have DAEMONS=(syslog-ng network netfs crond).
So I think the modules that aren't loading are probably apple-hid and/or usbhid, as rmmod-ing them in the live environment definitely kills the keyboard. I tried adding them to MODULES in /etc/rc.conf and even tried to add them with modprobe in /etc/rc.local, but nothing happens. Any ideas?
Sorry to resurrect an old post, but I came across something that might help.
I finally managed to get my 7,1 to boot into Arch and came across the same problem you have.
What got this working for me was to chroot into the system and remove the autodetect hook and then do: mkinitcpio -p kernel26
That gave me a bootable kernel (finally!) Also, I think the tty1 lockups might have to do with your keymap. I was having the same issue (even after booting into the working kernel) and could not type at all to login. I initially thought this had something to do with autodetect and was going about finding a way to get an older kernel on the system when I thought about the keymap setting in /etc/rc.conf. Sure enough mine was set to some appl derivative and when I changed it to "us" and rebooted everything was working!
Hope this can be of some help.