application doesn't quit but stays in tray

i'm writing a small irc client, my last problem was solved, but now i've a new one. when i quit the client i close all streams, close the socket and finally shut the socket down. then i close the application with Application.Exit(); but it isn't gone then, but remains in the system tray. any idea what went wrong? maybe a need destructors? but the garbage collector should delete the remaining content, shouldn't it? any idea?