Ckeditor "cke_button_off" property shows black screen

Hi,

i'm using CkEditor version 4 and i've been having problems lately in my application which im developing using richfaces for "IE8". there's a rich popupPanel on which i've used the ckeditor control. now when i hover on any of the controls like bold,italics, cut,copy,paste or indentation, the screen turns black in color.

When i investigated in IE developer console it was a problem with the property "cke_button_off" and "cke_button_on"

The same ckeditor works fine when it's put on the jsf form but when i include it in the rich popuppanel this problem occurs.

So when i remove this property by using removeClass() method in JQuery the problem seems to go away. But can you suggest another  way using which i could bypass this property to be set, so that the screen does not turn black and stays as is?

I'm attaching the screen shots so that you get a clear picture of what i'm trying to say. In te screen shot i've tried to hover over the controls "Italics" and the result is this screen. Any help regarding the same is appreciated.

Thanks in advance.