I use a natural table to format my page header. I have another natural table in the body. When the body's table is split onto the second page it interferes with the formatting of the header's table, but only the header-table on the first page. I've included an example. Run as-is, the header has the correct format. Uncomment the last row of the body table to see the incorrect header formatting. This behavior also occurs using live.contextgarden.net (today, 2013-05-21).

The incorrect header table format occurs with "split=yes" and "split=repeat" for the body table. If "split=no" then the header table keeps the correct format.

TexLive 2012 (updated 2013-05-20 to frozen version)
LuaTeX beta-0.70.2-2012052410
ConTeXt: 2012.05.30 11:26 MkIV fmt: 2012.9.13

\setuppapersize[letter][letter]
\setuplayout[topspace=0pt,
             header=42pt,
             headerdistance=6pt,
             ]
\setuppagenumbering[location=]
\setupwhitespace[none]
\define\syllabusheader{%
\vskip0.1mm
\bTABLE[frame=off,width=\textwidth]
  \setupTABLE[c][1][width=fit,  align=raggedright,style={\bfb\ss}]
  \setupTABLE[c][2][width=broad,align=center,     style={\bfd\ss}]
  \setupTABLE[c][3][width=fit,  align=raggedleft, style={\bfb\ss}]
  \bTR \bTD Left \eTD \bTD Center \eTD \bTD Right \eTD \eTR
\eTABLE
}
\setupheadertexts[{\framed[corner=09,width=broad,align=center,height=\headerheight]%
                          {\syllabusheader}}]
\starttext
\bTABLE[split=repeat]
  \setupTABLE[c][1][width=10em,align={center,lohi},style={\bfx}]
  \setupTABLE[r][1][align={hilo,center},style={\bfx}]
  \setupTABLE[c][2][width=20em,style={\tfx}]
  \bTABLEhead
   \bTR\bTH Row number \eTH\bTH Content \eTH\eTR
  \eTABLEhead
  \bTABLEbody
   \bTR\bTC  1 \eTC\bTC \input{knuth} \eTC\eTR
   \bTR\bTC  2 \eTC\bTC \input{knuth} \eTC\eTR
   \bTR\bTC  3 \eTC\bTC \input{knuth} \eTC\eTR
%   \bTR\bTC  4 \eTC\bTC \input{knuth} \eTC\eTR % Uncomment this line to see wrong behavior
  \eTABLEbody
\eTABLE
\stoptext