Cannot copy to Monodevelop

Windows 7 Unity 5.3

When I try to copy the code on the web page, I cannot copy it to Monodevelop.
Paste into Notepad for confirmation.

You can copy the code from Monodevelop to another Monodevelop source file.
You cannot paste a copy from Notepad into Monodevelop.

I don't remember changing the settings from the time I installed Unity.