Sorry for this innacurate email,
but I'm seeing something strange  with \underbar.
I'm using columnset with 2 columns,
and \underbar appear in a \section head customization.

luatex --vers
This is LuaTeX, Version snapshot-0.29.0-2008072308

ConTeXt  ver: 2008.05.21 15:21 MKIV  fmt: 2008.7.23  int: english/english


ASAP I will made an example.
-- 
luigi