That's because CKEditor is made with JavaScript. You'll have to modify your security settings in IE (even if you are using Mozilla). The idea behind it is that the browser doesn't make it possible for scripts (CKEditor) to access the user clipboard data, for privacy reasons.
Re: Cut, Copy and Paste security : works with other richtext
Customer and Community Manager, CKSource
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If you think you found a bug in CKEditor, read this!
Re: Cut, Copy and Paste security : works with other richtext
http://www-archive.mozilla.org/editor/midasdemo/
Re: Cut, Copy and Paste security : works with other richtext
https://addons.mozilla.org/en-US/firefo ... rd-helper/