Front Brake Rattle - ARGGGGHHHH!!!

[Zilverado]

First off - it's great to be back around again. Life has been pretty busy, and I have had very little time to snoop around. But finally I am driven back by necessity - a good thing (I guess).

Problem - Loose (rattling) inner brake pad on the driver's side front wheel.

Last year I did a fairly complete front brake job replacing everything except the rotors - they still were fine at that time.

Recently, a squeak along with a rattle developed on the left side. I checked it and found the brake pads to be loose and badly unevenly worn from front to back. The rotor seemed slightly warped, so I have now replaced the rotors as well as installed new pads.

Inner pad is still loose and rattle is still there. The inner pad is riding flush with the rotor (no visible gap), but I can push on the pad "tabs" down and it slides back and forth along the face of the rotor - causing the "tabs" to rattle against the caliper body.

So what is going on here? Is the caliper loosening off too much or applying uneven pressure? The retainer clip (inside the caliper piston, holding the inner pad) was not replaced. Could this clip be too loose? Am I missing some hardware?

Below are a couple of photos showing the installation and the area where I can move the pad.

Any help would be appreciated. BTW - it's great to be "home".