\emptylines is not producing empty lines. Here is the example from the 
wiki <http://wiki.contextgarden.net/Command/emptylines>:

\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