Missing data with Java Standard Tag Library

Hello,

I'm using Postgresql 7.3.2 and Tomcat 4.1.24.
When I'm trying to use the JSTL-tags (Java Standard Tag Library from apache.org) the result is something curios:
I'm getting the correct row count and a corresponding html-table, but there is no visible data on it.
Example from my jsp-page:
<p>Row Count: <c:out value='${mytable.rowCount}' /></p>
<table border='1'>
<tr>
<c:forEach var='${columnName}' items='${mytable.columnNames}' >
<th><c:out value='${columnName}' /></th>
</c:forEach>
</tr>
<tr>
<c:forEach var='${row}' items='${mytable.rows}' >
<td><c:out value='${row.acolumnname}' /></td>
</c:forEach>
</tr>
</table>

With this I got the exact <th></th> and <td></td> tags but no data between.
I tried Tomcat 5.0.5 and several prebuild jdbc-drivers from jdbc.postgresql.org, no success and no error message at all.

Thank you

Egon