@cmb:
@marvosa:
Very interesting…. I, however, did not modify any update settings.
System>Firmware, Updater Settings tab, you had "Use an unofficial server for firmware upgrades" set and a URL there. Often it's left over from when someone wants to follow snapshots. Then that config is restored to new hardware that's then running 64 bit, and on the next upgrade it obeys your update URL there and switches you to 32 bit.
That setting no longer exists in 2.3, but verify it on other pre-2.3 systems before you upgrade.
It's impossible to change architectures via auto-update if that box isn't checked.
I've been running PFsense since 2009 on v1.2.3 and can tell you without a shadow of a doubt that I have never upgraded to a Alpha/beta/RC/Dev release ever, so there would've been no reason for the auto-update url to be on anything but default as I only run stable releases.
Your explanation for how this issue could happen is completely rational, understandable and fits in the OP's case…. but I'm just saying if that is indeed what happened, the setting must have been flipped by some other process in the system because the auto-update URL was never modified manually in my case.