I moved your post to the
Help section because it exists to be used.
Alas, I have never encountered a problem with adding friends on GREE, but was the error that grey screen with a stern-looking face?

<- That is seriously the only "similar" emote I could express that with. If yes, all I can say is to fully close and reopen whatever application you were going through, or literally wait until another time. Since you posted this over a few days ago, has anything changed?