This is an old topic but wanted to answer this question as it will be coming up again in the not to distant future. We we first started off we had separate "login names" and "iczer names". After a few days we realized this is more trouble than anything else so we changed it. Most everyone who registered after launch, and those who "migrated" and account are fine. However, there are a few of you who still have different login id's and iczer names. Soon, next week I think, I am going to go through and make everyones login the same as their iczer name. I had announced this a while ago and then realized an extra level of complexity to it so I put it off and never let you all know.
In other news, if you can't use the "double login" fix thing, it's most likely because you are entering your login id, when it's asking for your "iczer name"... or... you have an "illegal character" in your name. The problem here is two fold. 1, you didn't read the instructions when registering and 2. I didn't test the registration component throughly enough. I'm looking into fixing this so it doesn't let anyone else register with an invalid name but I will most likely also have to change some peoples names in the game. We shall see.