Rather than disputing this with anyone, I'm going to make an inference.
It is a fact that with many online games lately, the connection appears to be good (good ms
reported, little lag) at the screen where one can accept a request to play and also at the start of the game, but as the game progresses, at inopportune times for just one player only, the action becomes choppy (meaning that it will be fast, then slow, then fast, then slower, then faster still, then slow, etc.). During the action for just one return shot, this cycle may repeat many times, such that as the player is approaching the point of contact and about to stop for proper positioning, the player may be just out of reach of the ball or too close to it at the point of contact. When the action is slow, keys have to pressed longer than normal in order to move the player properly; if the action becomes faster during positioning for a strike, then the keys don't have to be pressed very long, and so errors can occur easily. This issue also affects service strikes, for the same reason (one may press the keys too long due to the issue). Another fact is that this is becoming more frequent. Another fact is that this has nothing to do (at least on my system) with what programs are active on the computer of the one being affected (or with the Internet connection specifically). Another fact is that some players have basically admitted to causing this.
So, my inference is that some players in TE2009, as is common with other online games, are using network communication cheats and other means to disrupt the gameplay or their opponent. Here is a reference for your consideration:http://en.wikipedia.org/wiki/Cheating_in_online_games