Weird looking sky with a polarizer filter -- why?

[dmartinc]

Camera Canon EOS 5D Mark II
Exposure 1
Aperture f/16.0
Focal Length 27 mm
ISO Speed 100
Exposure Bias -1/3 EV

I used a circular polarizer to deepen the sky here. Tried different positions. But the sky has this weird look -- deep blue in the middle and whiter at the edges. Any ideas why this happened, or how to prevent it? This was taken at sunrise --
Any suggestions appreciated. Thanks

[IABoomer]

I just saw this on Phototuts about using polarizers. They suggest that using them on wide-angle lenses creates uneven polarization, which your above photo seems to prove.

Quick Tip: An Introduction to Polarizing Filters

[Sterling]

Polarizers provide maximum effect when facing 90 degrees to the sun. They have almost no effect when facing directly toward the sun or when facing 180 degrees away from the sun. By using such a wide angle, you have captured both some maximum effect part and some no effect parts of the sky.

[windrider86]

Your photo is gone! Can you replace it please