Checked it under the scope at work and still found no obvious cold solders or shorts. With most of the devices being fine pitch flat packs, 0402 discretes, or BGAs I can't even get to, decided re-flowing wasn't likely to yield results so just brought it home.
Was fiddling with it yesterday and decided I'd try to use older fw hoping that maybe there was a bad bit in the flash memory that might get twiddled, and when I hooked it up to my USB and powered it up, didn't all the lights come on after the confirmation beeps! I about lost my mind. I turned it off, put on just the screen, and powered back on and wasn't it sitting at the screen calibration! So I carefully put it all back together (after lubing up the wheel bearings and cleaning all screens) and it booted! I did the screen cal then was able to download my config in it. This doesn't feel like a cold solder to me, feels more like bad memory (RAM or flash) or bit flip kind of thing. Cold solders tend to be fairly permanent until rectified.
For those who also got stuck "in configuration mode", this appears to be the initial config which is done when no config/app exists, including the screen cal. That screams to me that the application got corrupted in memory somehow. Or possibly its own config settings in nvram.
So for now I'm back in business. I won't be powering it off ever again, unless the fw or config absolutely won't take and I have no choice.
