It´s embarassingly simple, but I´m puzzled and thought I ask before I try endlessly...
In addition I´m stubborn too, so I won´t just modernize the routine to circumvent the problem...

In my legacy app core I put records e.g. in

gaMy(1,1)="1"
gaMy(2,1)="2"

lstMy.RowSource=gaMy
lstMy.RowSourceType=5 - Array

Actually it can´t get more primitive. I can see the two array elements in the debugger, but only one in the Listbox.
< arrrggghh >
G