Do you have a row (or rows) selected when you apply the command? The heading
row must be the top row in the table (you can tag more than one row, but
they have to be adjacent rows at the top of the table), and the table must
not be wrapped.
Note that Table | Heading Rows Repeat in Word 2003 is straightforward
enough. Word 2007 is a little more confusing because the Header Row check
box on the contextual Table Tools | Design tab merely tells Word that the
first row in the table should have the formatting specified for a heading
row. To make the heading row repeat, you have click Repeat Header Rows on
the Table Tools | Layout tab.
--
Suzanne S. Barnhill
Microsoft MVP (Word)
Words into Type
Fairhope, Alabama USA
http://word.mvps.org