Ok, I notice that when I do certain movements...one in particular is a shin block, basically raising your knee up in the air so that your shin would block an oncoming kick...my hip emits a popping sound. Now I understand that sometimes joint popping is simply gas emmission but I was perusing a website that had popping hip listed under some of it's problem areas for martial arts types. Basically much of what is said (I'll copy and paste below) seems very applicable to me. I used to play tennis quite often and I feel that my hip flexors are quite weak as well. Recently I've added the abductor and adductor or whatever those girlie machines are at the gym that spread your legs out...basically if anyone has experience with this problem and could offer any other training advice that would be cool. Here's this one guy's explanation:

Popping Hip is more typically found with tennis players who may use distance training to increase endurance. You should read the balance of the hip section to understand the complex interrelationship between the lower back, hip, quads, and hamstrings. Typically associated with runners, it can also be a product of tennis, which can evolve into popping hip. This problem is generally the result of the violent and recurring trunk twisting, knee bending, and hip rotation required by the sport. This results in tightness in the muscles of the lower back including the quadratus lumborum, the psoas, the external obliques, the tensor fascae latae, the erectae spinae, the gluts and the iliotibial band . Not only is the area tight and difficult to stretch, but, in many cases, the area requiring adduction and abduction is weak.

Many of these muscles attach around the greater trochanter (the bony prominence of the lateral part of femur). These muscles become extremely tight. The overuse of these unstretched, overused and weak muscles can also give rise to trochanteric bursitis which just aggravates the whole problem. Rest, proper stretching, icing, strengthened these ignored muscles, and massage and/or rolfing can lead you on the way to recovery. It takes years to create this obnoxious, little understood condition, and it takes time to strengthen and lengthen the muscles of the area. Since X-rays do not reveal the condition (and will not show degenerative hip arthritis), most orthopedic surgeons will not recognize the condition.

Lemme know if you have any further thoughts...or if this guy is just full of bs or not.