Hi
Thanks for bringing that to my attention.
Seams that Webzen has taken it down.
To my knowledge that means you can no longer transfer any remaining gPotato ID's yourself, you'll have to open a support ticket about it.
http://support.my.com/games/formTicket/?&questionId=54
is the closest ticket template for it.
I'll talk to me bosses tomorrow and double check how we go from here regarding any un-transfered accounts.
-Wraith