The quick brown fox jumps over the lazy dog.
Note: the same inappropriate layout problem (underline too high and too thick) also happens with "MS Serif" and "MS Sans Serif" fonts. Credit must go to Philip A. Hagen for discovering and reporting this layout issue. Credit must go to a certain "iecustomizer" for forwarding and validating this issue into IE beta feedback bug 408071 webpage.
This bug has been reported at connect's IE beta feedback as bug 408071.
Update: this bug has been FIXED in Internet Explorer 8 final release build 6001.18702 released on March 19th 2009. Otherwise, Internet Explorer 8 final release build 6001.18702 PASSES this specific and particular testcase.