Cannot login via xdm after fresh install

[Erkki Ruohtula <erkkiruohtula%yahoo.com@localhost>]

Hi,
I did a fresh installation with NetBSD-7.1-amd64.iso in VirtualBox
5.1.26, mostly using defaults. I did enable xdm in the installer.
Everything appeared to go smoothly, and the system now starts nicely
X11, and shows the xdm login screen. The problem is I cannot get
past that. If I enter the username root and its correct
password, I get a dialog box labeled "Session Menu",
with text "chooseSessionListWidget" and buttons under it,
of which most are grayed except "Default/Fail Safe" and "Cancel".

I thought "Default/Fail Safe" would be the obvious choice, but if
I hit it, I get a black screen, except for the console log window
in lower right-hand corner. X11 seems to be still running, but
it is impossible to do anything except reset the (virtual) machine.
Is the fail safe  configuration missing? Should something
special be chosen in the installer? (in other X11 installations
I have seen it usually consist of starting twm and a xterm window).

Erkki

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