Bizarre IE checkbox bug?

Question

I have some perfectly mundane code that puts 4 check-boxes in a 2x2 table. In Internet Explorer (but not in Firefox,Chrome,Opera, or Safari) the the two rightmost check-boxes will not toggle on and off. Well, they do, rarely, but only in a random haphazard manner. Please note that I have no JavaScript triggers associated with these checkboxes.

Now the kicker: if I move the table containing the checkboxes outside of its containing table, the check-boxes work fine.

Why the rightmost boxes? Why only in IE? It's bizarre. The code for the inner table is below.

Skolem

<table>
  <tr>
    <td>
      <input type="checkbox" name="a" value="1">Accepted
    </td>
    <td>
      <input type="checkbox" name="b" value="1">Cancelled
    </td>
  </tr>
  <tr>
    <td>
      <input type="checkbox" name="c" value="1">Complete
    </td>
    <td>
      <input type="checkbox" name="d" value="1">Closed
    </td>
  </tr>
</table>