plugin not working on intellij 15.0

Hello,
I have a plugin that I modified that is used to work properly on intellij 14.1.6 and on intellij 15.0

I tried to split it into 2 version of code and fixed some bugs.

now the 14.1.6 version is working properly but I can get the 15.0 version to work.

I keep getting an error:
09:48:16 <server_name> Server: Access is allowed from event dispatch thread only.

do you what is the meaning of this?
when I debug in on intellij community 15.0.2 and it works ok but when I try to activate it on 15.0 ultimate I keep getting this error.