Originally, rangers were able to perform something called "jumpshot" by jumping and using skills at the same time, which allowed them to use up to 3 skills under 1 second. Everytime a macro bug emerged that just made it easier to do this, NCsoft responded a patch. However, despite two patches, NCsoft failed to address the core problem; jump shoting. It was rumored that jumpshot was purposely added into the game as a way of balancing rangers. However, letting this "jumpshot" exist has produced yet another bug in the game.
Players noticed that jump shotting not only lets them use 3 skills at once, but also lets them use combo skills in any order.
For example, skill A needs to be used in order to use Combo Skill B or C. The game normally only allows you to perform AB or AC. When you use B or C you return to the initial status, requiring skill A to be used again in order for B or C to be used. However, by jumpshotting you can perform ABC or ACB, clearly not what NCsoft had in mind.
Orignal Post with Videos
It seems that NCsoft needs to fix the jump shot itself, a problem dating back to Open Beta, in order to prevent further bugs from emerging. Many players are demanding a fix to this exploit and a real balancing patch for rangers.