I'm also having this problem. The game in which in trying to us AR codes for is Phantasy Star Online episode 1 & 2 both regular vs. and Plus vs. I'm using dolphin 3.5, 4.0 and 5.0 all of which is not working for me and i'm sooo lost as to what to do. watched numerous vids about adding codes, and yes i have cheats enabled in the config how ever in version 5.0 it tells me that I don't need the Master code but when i try to use a basic code such as max meseta it doesn't work nor any other code. Someone please help me!! On the older versions the master code that I'm trying to use doesn't work as well as any other code. I don't know or understand how gecko codes work due to it saying i failed to download the codes whenever i tried... Honestly don't know what to do!! 
