Popping sound?

My printer is making a popping sound when it travels on the X axis. I can't pinpoint the exact location of the sound. I'm not sure if it's gears feeding the filament or just the plastic moving from the vibrations of the movement of the printer head. It just started happening a couple days ago. Does anyone have any idea what that could be? I uploaded a sample video, it's in zip format as I can't upload a .MOV to the forum.

EDIT: I guess the uploads isn't working. Here is a link to the video:

 

More than likely a bearing has a frozen ball possibly from hairspray. The best thing to do is turn off the motors and run the print head all around until you "feel" the drag. I would change all of the bearings except for the sleeve bearings which would not cause this problem. They are all available at Partsbuilt.com and they are higher quality than the original..