This is a quirky problem with a few answers depending on the source of the issue. Before you try any of these, just make sure your Esc key isn't stuck down. That's the easiest fix
General Fix #1: See http

/www.pcreview.co.uk/forums/re-copy-and-paste-not-working-t2287121.html. Use the suggested app to check your clipboard for problems.
General Fix #2: Go to registry HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\. Delete the graphic number ( a square or an L) located before zone number 0.
General Fix #3: Look for "Send to Bluetooth" add-in under each office program and delete it. Find it under Options, Add-ins. If it's not listed, you don't have the add-in and it's not the problem. If you see it, go to Manage, Select COM add-ins and click Go. Check the box next to the add in and click Remove.
General Fix #4: Click the Start/Windows button, Type Go to Start (Start/Run) type the following in the search box: cmd /c “echo off | clip” then hit Enter. Note there is a space between "cmd" and "/" but nowhere else. I keep a copy of this command in my stickies on ClipX so I don't have to go back and find it every time this happens.
General Fix #5: Make sure you are using the most recent version of Flash Player. If not, update it.
If you use Remote Desktop: Open task manager, end the RDPCLIP.EXE process, and then restart the task. To restart the task, go to applications tab, click new task and type in rdpclip.exe.
If you use Advanced System Care 5 from IOBIT (ASC): Open the ASC Toolbox. Under Optimize, Smart RAM, Settings, uncheck "Clean Clipboard"
If You use Skype: Delete the Add-ins for IE and Firefox (Skype might also cause problems when using the Click to Call feature in Chrome).
If the problem occurs in IE: Go to Internet Options, Advanced tab. Click Reset under Reset Internet Explorer Settings. Click OK. This fixes problems associated with malware.
If you recently installed Microsoft visual C++ 2005 (needed by some programs to work): Try uninstalling it if you don't absolutely need it. If you do need it, try General Fix #4 (the one that ultimately worked for me).
If you use Adobe Acrobat: Try uninstalling it. Might need to use Foxit Reader instead.
Good Luck!