Not human error.
That happened to me on my vs640 about 2 months ago. Never seen anything like it in a year and a bit, then I got 2 of those funny garbage data things in the space of 2 weeks.
I don't know if it has anything to do with it, but since then, there have been around 3 firmware updates. I haven't had one since those 2, so it could have been a FW bug... who knows.
What version FW are you running? You can tell by double clicking the printer graphic in VW.
Latest is 4.1.
Your VW should be 4.5.