Booting linux guest stops at BIOS message on window

[robztesting]

I have been building Chromium images for a week, then one day the images stopped completing the boot cycle. The last thing I see on the screen is:

EXTLINUX 3.83 2009-10-05 ECIOS Copyright (C) 1994-2009 H. Peter Anvin et al

I have compared the VB logs from a good boot cycle and hung one, there doesn't appear to be any significant differences. Or, at least to my untrained eyes I don't see any.

Could someone provide some advice on how to debug this issue?

Unless I missed anything, here's the boot log from a hung attempt:

Modedit: removed log, either use code blocks, or use pastebin. Posting long pieces of text with no option to compact it is bad nettiquette and can result in official warnings and even a ban.