<div>
<div><font face="Arial" size="2">I have the same problem typesetting Syriac in two colums. Can you show me a simple example how to use your fix?</font></div>
<div><font face="Arial" size="2">I am using this preamble:</font></div>
<div><font face="Arial" size="2">\documentclass[12pt, twocolumn]{article}<br>\usepackage{xltxtra, polyglossia}<br>\usepackage{bidi}</font></div>
<div> </div>
<div><font face="Arial" size="2">% font selection stuff </font></div>
<div><font face="Arial" size="2">etc.</font></div>
<div> </div>
<div> </div>
<div><pre>Hi everyone,
Currently bidi has no command for changing the direction in two columns texts.
This problem even affect index part of a text because index part is typesseted
in two columns. I tried the following patch (which is, I think, from rlbabel)
and it solves the problem

%%%%%%%%For Right-to-Left two column command, I guess taken from rlbabel
\let\@<a href="http://tug.org/mailman/listinfo/xetex">old at outputdblcol</a>\@outputdblcol
\newcommand{\<a href="http://tug.org/mailman/listinfo/xetex">rl at outputdblcol</a>}{%
 \<a href="http://tug.org/mailman/listinfo/xetex">if at firstcolumn</a>
   \global \@firstcolumnfalse
    \global \setbox\@leftcolumn \box\@outputbox
  \else
    \global \@firstcolumntrue
    \setbox\@outputbox \vbox {\<a href="http://tug.org/mailman/listinfo/xetex">hb at xt</a>@\textwidth {%
                              \hskip\columnwidth%
                              \hfil\vrule\@width\columnseprule\hfil
                              \<a href="http://tug.org/mailman/listinfo/xetex">hb at xt</a>@\columnwidth {%
                                \box\@leftcolumn \hss}%
                              \<a href="http://tug.org/mailman/listinfo/xetex">hb at xt</a>@\columnwidth {%
                                \hskip-\textwidth%
                                \box\@outputbox \hss}%
                              \hskip\columnsep%
                              \hskip\columnwidth}}%
    \@combinedblfloats
    \@outputpage
    \begingroup
      \@dblfloatplacement
      \@startdblcolumn
      \@whilesw\<a href="http://tug.org/mailman/listinfo/xetex">if at fcolmade</a> \fi
        {\@outputpage
         \@startdblcolumn}%
    \endgroup
 \fi}
\newcommand{\rldblcolumn}{\renewcommand{\@outputdblcol}{\<a href="http://tug.org/mailman/listinfo/xetex">rl at outputdblcol</a>}}
\newcommand{\lrdblcolumn}{\renewcommand{\@outputdblcol}{\@<a href="http://tug.org/mailman/listinfo/xetex">old at outputdblcol</a>}}
%set the default direction of the twocolumn texts to Right-to-Left
\rldblcolumn
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Also I think changing 

\def\underline#1{\@@@underline{\<a href="http://tug.org/mailman/listinfo/xetex">if at rl</a>\RL{#1}\else #1\fi}}

in bidi to 

\def\underline#1{\@@@underline{\ifmmode #1\else\<a href="http://tug.org/mailman/listinfo/xetex">if at rl</a>\RL{#1}\else #1\fi\fi}}

makes bidi more stable with underline texts.

</pre></div></div>
<div> </div>
<div> </div>