I got the following error in the minimal example (which is all shown in the output below)<div><br></div><div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">system          &gt; tex &gt; error on line 4 in file simpl.tex: Undefined control sequence ...</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap"><br></span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">1     \setuphead[section][before={\column}]</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">2     \starttext</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">3     \startcolumns[n=2]</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">4 &gt;&gt;  \section{this is a section}</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">5     \section{another section in a new column}</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">6     \stopcolumns</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">7     \stoptext</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">8     </span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap"><br></span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap"><br></span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">\208&gt;multicolumn:yes -&gt;\par {\testrulewidth </span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                                            \zeropoint \ruledvskip \textheig...</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">\page_breaks_columns_process ...dle_direct \v!yes </span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                                                  \fi \relax \the \everyafte...</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">&lt;to be read again&gt; </span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                   \relax </span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">\dohandleheadpagebreakyes ...ter \c!before \relax </span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                                                  \doif {\headparameter \c!a...</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">\docheckheadbefore ...se \continuoussectionhead #1</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                                                  \fi </span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">\doheadspacingbeforeyes ...handleheadpagebreakyes </span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">                                                  \headparameter \c!inbetwee...</span></font></div><div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">...</span></font></div>
<div><font color="#222222" face="courier new, monospace"><span style="white-space:nowrap">l.4 \section{this is a section}</span></font></div></div><div><br></div><div>Basically, the first line in the file introduces the error.  It worked a few weeks ago.</div>