Hi Pau, Owner of a Thinkpad x220 here. As far as I can remember, my laptop does actually 'freeze' for a few minutes when booting from usb flash drive. This does not happen after installation.
Please wait around 5-10 minutes or more, everything should work fine after that. Regards, Alex P.S. I use Thinkpad x220 + OpenBSD 5.1 as my primary development machine. Many thanks to people, who made that possible!
