\emptylines is not producing empty lines. Here is the example from the wiki:
\setuppapersize[A5]
\startcolumns[n=3]
    With non-empty lines\crlf
    asdf\crlf
    asdf\crlf
    asdf\crlf
    asdf
\column
    With \tex{emptylines[2]}
    \emptylines[2]
    asdf\crlf
    asdf
\column
    With \tex{blank[2*big]}
    \blank[2*big]
    asdf\crlf
    asdf
\stopcolumns
and here is the output using the current MKIV beta:

--
Rik