I have the same problem on this computer - my other one (also W7 + Office 2010) works fine. Both are completely up to date with MS patches and service packs etc.
To clarify, can only paste plain test or Unicode if either IE9 or Chrome is open. This PC had a clean install 3 days ago. If you want to know why, look at my blog at http://christitcumb.wordpress.com/
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