There was a thread about columns and whitespace ~ 2 weeks ago, but I wasn't a subscriber then. I've just come across it independently myself. I'm not sure what conclusion was come to. From a few tests, I'd characterize the problem code in \startcolumns as: "if whitespace has been set to more than none, set whitespace to 'line'."
Try it by uncommenting various lines:
%\setupwhitespace[none]
%\setupwhitespace[small]
\starttext
\startcolumns[n=2]
%\setupwhitespace[small]
\input knuth
\stopcolumns
\stoptext
Do people agree with that characterization; has the bug been found; what's being done about it? I don't want to have to re-setup whitespace every time I go to columns.
James