Ceramic brake squeal ...

Hi all,
I have an '00 Cirrus and '05 Grand Caravan; both at 90K mi. The
original front and rear brake pads on both vehicles were getting thin,
so I elected to change them in May '09. I bought and installed high-
quality Wagner rotors and ceramic pads. The original pads were worn
evenly on all four corners of both cars. Installation was
straightforward, but I've developed a problem.

While I applied brake grease on the backing plate contact areas during
installation, the front brakes on the '05 GC squeal at low speed/light
pedal pressure ... like idling through a fast food drive-thru. The
rotors look good, the pads are fine, but something is squeaking.
Again, this is dependent on speed and pedal pressure. Seems as though
the pad simply squeals when clamped against the rotor under light
pressure, but it is annoying as hell. Because I can rule out most of
the issues I'd think to look at, I'm stuck in my thinking.

Thanks for your suggestions in advance,
Chris