Thanks for the replies. I suspect this is the answer I needed: don't try to install a 6.2 snapshot just before version 6.3 is released, instead wait for the release and install that.
> You need to be sure to use the bsd.rd from the snapshot! I'm pretty sure that's what I booted. Does any other bsd.rd have a default path of pub/OpenBSD/6.3/i386? > You say install, which is very different from upgrade. I'm running 6.1 on my laptop hard disk, and I wanted to install a recent snapshot to a USB key. The back story involves an upgrade to 6.2 stable, a kernel failure whenever I started X Windows, and a desire to reproduce the fault while preserving a bootable system on the hard disk. I'll wait for the 6.3 release, and see if X still crashes the kernel. Thanks again Rodney