customized mode-line face interfers with gnus keybinding

[Darren Hoo]

customize face mode-line as following

(custom-set-faces
 '(mode-line ((t (:box (:line-width 1 :style released-button))))))

Then in Gnus's Summary buffer hitting RET will scroll down the 
article one page as SPC does instead of one line down, while M-RET
is ok(one line scrollup).

I experience this wierd behavior when using gnus with color-theme-arjen
and track down the problem to the customized mode-line face above.

This is always reproducable both with emacs23 and emacs24 trunk.

--
Darren