Hi Hans,
Yes I can see others have found the same problem. But thanks anyway for the link, because it prompted me to experiment with a box. At least for \startsimplecolumns .. \stopsimplecolumns there seems to be hope. See the example below, the last framedtext has two columns inside. For \startcolumns .. \stopcolumns this is not a solution: an error message about \prevdepth appears.
Normal columns need the output routine and won't work inside of a box, streams are a way to invoke the output routine. Simplecolumns are simpler and don't need the output routine, it's just a simple vsplit and work in a few cases but is more limited, this is why it did work, the internal function is like this. \starttext \setbox0=\vbox{\hsize.45\hsize\input knuth\par} \setbox1=\vsplit0 to .5\ht0 \hbox to\hsize{\box1\hfill\box0} \stoptext Wolfgang