I too had problems applying some of the updates from a few months ago, ending up with a non bootable uSD card. This was even when I carefully followed the posted instructions on the Arch website. That was starting with an image from September 2012.
I'd suggest starting from scratch if you can. I didn't have a problem booting from a fresh Arch image from Aug 2013, other than the fact it is now based on a 3.x kernel, and several hardware drivers no longer work as they did in 2.6.
This update stability is one of the downsides of Arch, and noted in their documentation. If you want a more stable environment, you could try OpenWRT - another lightweight distro - but that is just going to move your pain points to other areas.
Kean