w7 as vBox guest Firefox installation horror

Instead of installation being a matter of seconds, this popup starts spooling numbers into astronomical ranges, I mean like the 100,000 regime. I haven't installed a firefox into no window for ages but this spooked me right into a hard abort TWICE now! As a minimum the devs could annunciate what it's all about, but NO, it just keeps doing files and folders and with a frozen progress-bar half way seemingly not intent on ever stopping.

Sorry about the image being bad, it was a screenshot and I have no idea how it became unreadable.
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