Recipient-unavailable(404)

I am using server : programmer-art.org

I keep having recipient-unavailable(404) exception during join.

Here is the code snippet :

if (muc.isJoined() == false)
{
try {
muc.join(username);
} catch (XMPPException ex) {
log.error(null, ex);

http://jstock.cvs.sourceforge.net/viewvc/jstock/jstock/src/org/yccheok/jstock/ch at/ChatServiceManager.java?revision=1.5&view=markup

I do not have problem in state Connecting and Account Creating.

However, when come to Room Creating, those are the problem occur, and I keep receiving meesage from server :

yccheok81 left the room.

yccheok81 left the room.

yccheok81 left the room.

yccheok81 left the room.

yccheok81 left the room.

Here is the exception trace :

SEVERE: null
recipient-unavailable(404)
at org.jivesoftware.smackx.muc.MultiUserChat.join(MultiUserChat.java:471)
at org.jivesoftware.smackx.muc.MultiUserChat.join(MultiUserChat.java:362)
at org.yccheok.jstock.chat.ChatServiceManager$ChatService.room_creating(ChatServic eManager.java:274)
at org.yccheok.jstock.chat.ChatServiceManager$ChatService.run(ChatServiceManager.j ava:128)
at java.lang.Thread.run(Thread.java:619)