I installed 5.2 on my amd64 laptop. I'm using the altroot softraid method of encrypting /, posted by Nick on geekyschmidt.com. Anyway, the first boot hung on "cpu3: AMD erratum 721 detected and fixed". I powered off and rebooted, and haven't had a problem since. I'm not able to reproduce it, so I don't think further details are warranted.
I'm reporting this just in case others encounter this issue. P.S. Thanks very much for the new pthreads. It's working great.
