It was actually a region screenshot with ksnapshot (not sure why I did that rather than File->Save Image, which if I use "Exact Copy of Window" should give me exactly what I get on the screen).
I have a few problems with the fonts on my laptop - this is related to some font limitations in the Qt infrastructure we're using - so whilst the UI suggested that the plots you were seeing were using Helvetica, they weren't really (as you can see there are some serifs on the fonts).
I normally use this bit of code to try fixing up my fonts - they actually set them to the default values:
let((curVal toolpartition pat)
foreach(partition '(axis horizMarker referenceLineMarker vertMarker pointMarker
refPointMarker specMarker interceptMarker circleMarker multiDeltaMarker
transEdgeMarker graphLabel probe polarGrid smithGrid)
sprintf(toolpartition "viva.%s" partition)
printf("replacing %s font\n" toolpartition)
envSetVal(toolpartition "font" 'string
pcreReplace(pat curVal "Helvetica" 1)
Here's a resulting Save Image from having picked the above.