This answer is a little bit late, but maybe someone is still playing around with the K2:
I had the same problem as the threadstarter. After upgrading to 3.2.1 I could not register my kindle. To bad I didn't saved a copy of "/var/local/java/prefs/reginfo" before upgrading :-(
I found no way to get Internet access for registration with USB-networking (usbQa is not supported anymore in 3.2.1), and I also could not find the files for the "registration hacks"..
After all this stuff which did not work, here comes the simple solution: I simply copied the reginfo file from a working K3 to my K2. Of course USB-networking ist necessary for this. Quite likely you don't even need a valid "reginfo". It might be enough to fill out some fields in it (this is described here:
https://www.mobileread.com/forums/sho...4&postcount=17).
Good luck!