Written in 2011 – http://myitforum.com/myitforumwp/2012/06/19/resolved-microsoft-office-copy-and-paste-stopped-keeping-source-formatting-if-skype-click-to-call-is-installed/
I noticed recently that my copy and paste in Microsoft Office 2010 stopped keeping the source formatting. It was only allowing the paste of text only. If you were to check for paste special it would show only a capital A.
I noticed that if you closed all internet browsers except Firefox the issue would resolve.
Turns out SKYPE Click to Call Plug in is causing the issue
Uninstall SKYPE Click to Call.
Everything works well again!