something wrong with my client?

[MoToRoLa]

No, NoV was right, you must aim BEHIND the players

its not true if they run in line you d never shoot them if you shoot behind 
you must shoot in front when they are running in line, and behind, when you have tracked the route of the enemie, so when you think he is about to turn, you shoot behind

[Markz]

Here's that help video for your problem. http://forum.sa-mp.nl/index.php?topic=8192.0