Operating System: Windows 7 Professional 64 bits
Adobe Reader Vesion: XI
That error is very easy to reproduce: select two or more lines of a pdf document and press "cntl + C" several times in repetition. Frequently 4 ou 5 followed repetitions trigger that issue. A curious thing happens when "cntl + C" starts to fail: the copying process through "Edit > Copy" menu still works. But if you try repeated times to copying through "Edit > Copy" menu, then this method also starts to fail too, but at the same time of this failure, "cntrl + c" starts to work again (it is like a seesaw).
My computer has no skype plugin installed, so the skype plugin + Internet Explorer is not the root cause of that issue.
This problem occurs even if I am running only Adobe Reader XI application, i. e., without start Internet Explorer, or any office application, or windows live messenger, or skype, etc.