It couldn't hurt to try uninstalling your anti-virus program. Someone recently had a conflict with Securom and their DVD drive when Panda Antivirus was installed (and an error after authentication if they tried an external drive), and needed to uninstall it: see Emulator detected
Maybe try booting into Safe Mode (reboot, hit / hold down F8 as Windows starts to load, before the splash screen, and in the menu that comes up, select 'Safe Mode with Networking') and see if the game or manual activation will work in safe mode, and if so, if you get the same problem trying to enter the code. The game itself will probably not run, but might trigger the activation program if you try.
Did you email email@example.com? It's the weekend there now, though.