It looks like you probably have a pre-production YubiKey NEO (See here:
http://www.yubico.com/2014/04/yubikey-neo-manager-application/). More specifically from that page,
Quote:
The NEO Manager cannot be used to manage NEO applets with Production version YubiKey NEOs. If your YubiKey NEO has a serial number of 3,000,000 or above, you will not be able use the YubiKey NEO Manager to view, load, reload or remove NEO Applets.
To install applets, you need to change your connection mode to "HID + CCID with touch-eject". You should then be able to install applets.