Williams was trailing Clijsters 4-6, 5-6 and serving at 15-30 when the baseline judge called a foot-fault on a second serve.

CNN: Serena handed suspended ban and fine

That 6-4 7-5 semifinal win was not without controversy, as Williams lost the match after receiving a point penalty on match point for verbally abusing a line judge over a foot-fault call.

CNN: Unseeded Clijsters secures U.S. Open victory

Replays indicated that the line judge may have got the foot fault call wrong.

CNN: Serena handed suspended ban and fine