The default value for the page size settings (Layout->Pagesettings: Two sided) lets my laser printer goto to error stop

The templates for new score creation don't appear to have a page setting explicitly set and MuseScore by default (I don't know why other than that it has to have some sort of default behaviour) assumes two-page setting. I presume that your printer (or the printer driver) isn't handling the request for duplex printing properly (i.e. it should revert to single page printing if it isn't a duplex printer). Possible solutions:

1] Every time you create a new score, manually uncheck the two-sided print box.
2] Create a new score, uncheck the two-sided box and save it as a template so that when you create a new score next time it is set up correctly. This has the added advantage in that if you often write for a particular instrument/group of instruments you can save yourself a bit of work each time you create a new score.
3] Internet search and update printer driver if it is a known issue with other programs.

Attached is an example template I use for piano scores. It's just a blank piano template with 100 measures and the two-page setting turned off. If you look in MuseScore Edit->Preferences you can find the directory where your templates are stored and place any new templates there.