I have attempted to claim 2 of the more recent Key Codes (Webzen; Wartune Reborn), but each time I tried I received the response:
There was an unknown error retrieving your key. Please leave a message on the Forums and we will get back in touch with you as soon as we can.
This is the first time this has happened to me, and I have claimed several keys for other games in the past, without issue or complications.