Spoiler!
Was a result of switching over PCs to a newly installed OS. Time was set for 6:29pm when it was 6:19pm. Oddly enough, that was while it was set to Pacific time while I'm in Eastern. Going by debug file, Core correctly guessed my time zone and noted a 179 minute discrepency (which isn't quite right, either), which I find really odd, though less than the useless hard hang.
In case I attracted a dev... why does Core go from a loading splash screen to being invisible (less tray icon) and unclickable for ~5 minutes on loading?
ETA: Actually... I take it back. It may be out of space.... I'll see if it does it again. I still have windows.old on it -- wasn't a fresh install, and haven't sorted through what I need and don't on the SSD, though datadir is set to a separate hard drive... don't think it ran out of space, but I'll wait to confirm.
