Clicking on a checkbox with the following Selenium command in HTML-mode:

click $Checkbox$5

does not do anything for the following HTML fragment that uses the <label> HTML element:

<tr>
  <td colspan="2">
    <label>
      <input type="checkbox" name="$Checkbox$5"/>
      <img src="draft.png" border="0"/>
      text
    </label>
  </td>
</tr>

If I remove <label>, Selenium works ok.