Thanks for the responses Worker and Gustavo.
To test your suggestions, I restarted my computer and opened PLD, Notepad, and Internet Explorer (IE only to get to this forum).
Surprisingly, copying and pasting seems to work from PLD to notepad, from notepad to PLD, and from PLD to PLD.
I proceeded to open Microsoft Outlook and test copying and pasting in Outlook, and then again with PLD. Everything seems to work still.
I'm going to continue testing with other Microsoft Office applications that I use heavily and see if I can identify the cause.
Thanks a lot for the responses. Very well could be a "smart" Office clipboard issue.