Corrected changes who made the AdHoc MUC crashing:

- room name set to null in ConferenceChatManager
- use of a ChatRoomMember (from a ChatContact) in ChatContactCellRenderer

src/net/java/sip/communicator/impl/gui/main/chat/conference/ChatContactCellRenderer.java

@@ -53,8 +53,10 @@ public Component getListCellRendererComponent(  JList list,
         this.rightLabel.setIcon(null);
 
         final ChatContact chatContact = (ChatContact) value;
-        final ChatRoomMember member 
-            = (ChatRoomMember) chatContact.getDescriptor();
+        ChatRoomMember member = null;
+        
+        if (chatContact.getDescriptor() instanceof ChatRoomMember)
+        	member = (ChatRoomMember) chatContact.getDescriptor();
 
         this.setPreferredSize(new Dimension(20, 30));
 
@@ -69,9 +71,10 @@ public Component getListCellRendererComponent(  JList list,
         this.nameLabel.setFont(this.getFont().deriveFont(Font.PLAIN));
         this.nameLabel.setText(displayName);
 
-        if(member.getRole() != null)
-            this.nameLabel.setIcon(
-                ChatContactRoleIcon.getRoleIcon(member.getRole()));
+        if(member != null)
+        	if(member.getRole() != null)
+        		this.nameLabel.setIcon(
+        				ChatContactRoleIcon.getRoleIcon(member.getRole()));
 
         if (contactForegroundColor != null)
             this.nameLabel.setForeground(contactForegroundColor);
@@ -82,7 +85,7 @@ public Component getListCellRendererComponent(  JList list,
 
         if (avatar != null)
             this.rightLabel.setIcon(avatar);
-        else
+        else if (member != null)
         {
             if(chatContact.getName().equals(
                     member.getChatRoom().getUserNickname()))

src/net/java/sip/communicator/impl/gui/main/chat/conference/ConferenceChatManager.java

@@ -24,7 +24,7 @@
 import net.java.sip.communicator.util.*;
 
 // Java 1.6 has javax.swing.SwingWorker so we have to disambiguate.
-import org.jdesktop.swingworker.SwingWorker;
+import org.jdesktop.swingworker.*;
 import org.osgi.framework.*;
 
 /**
@@ -793,7 +793,10 @@ public AdHocChatRoomWrapper createAdHocChatRoom(
                 members.add(opSet.findContactByID(contact));
             }
 
-            chatRoom = groupChatOpSet.createAdHocChatRoom(null, members);
+            
+            chatRoom = groupChatOpSet.createAdHocChatRoom(
+            		"chatroom-" + new Date().getTime(),
+            		members);
         }
         catch (OperationFailedException ex)
         {