CSS declaration "vertical-align: middle;" is incorrectly rendered in Internet Explorer 8

Actual result (live result in your browser):

vertical-align: middle x

Expected result (screen shot):

Reference:
"middle
    Align the vertical midpoint of the box with the baseline of the parent box plus half the x-height of the parent."
CSS 2.1, section 10.8.1, vertical-align property

This testcase is rendered as expected with NS 6.1, NS 6.2, NS 7.0, NS 7.1, NS 7.2, Firefox 2.0.0.3, Seamonkey 1.x, Seamonkey 2.x, Epiphany 2.14, Safari 2.0.4, Safari 3.0.4 and Konqueror 3.5.5. Opera 9.26 and Opera 9.50 almost pass this test.