Yet another "what's that sound" question

This weekend, I started geting an odd popping sound in my '00 XJ Sport (stock except for new tires) What happens is when I back up (out of the drive way) and press the brakes I hear two pops that come from the front suspension. Then, the first time I have to stop after starting forward, it happens again. It only happens after changing direction of travel. Any thoughts/ideas? I have checked that the brakes aren't loose but don't have any ideas of what to check after that. Any assistance is appreciated. Thanks

I have had that before, and I got under and tightened down all 4 of the big lower control arm bolts and that fixed it. Hope that helps you.