Minibuffer size in emacs increasing on changing the default font

Hi I was开发者_开发问答 changing my default font in emacs. Suddenly, the size of the minibuffer is becoming huge occupying 1/4 of the screenspace. This happens whenever I change my default font.

How do I correct this? (See Screenshot). I am using Emacs 23.1.1

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Sounds like a bug. `M-x report-emacs-bug'.