diff --git a/src/net/java/sip/communicator/impl/protocol/jabber/OperationSetPersistentPresenceJabberImpl.java b/src/net/java/sip/communicator/impl/protocol/jabber/OperationSetPersistentPresenceJabberImpl.java
index 9dbc90bb5..ffe410396 100644
--- a/src/net/java/sip/communicator/impl/protocol/jabber/OperationSetPersistentPresenceJabberImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/jabber/OperationSetPersistentPresenceJabberImpl.java
@@ -962,10 +962,14 @@ else if(evt.getNewState() == RegistrationState.UNREGISTERED
                 ssContactList.cleanup();
                 subscribtionPacketListener = null;
 
-                if(parentProvider.getConnection() != null &&
-                    parentProvider.getConnection().getRoster() != null)
-                    parentProvider.getConnection().getRoster()
+                XMPPConnection connection = parentProvider.getConnection();
+                if(connection != null)
+                {
+                    // the roster is guaranteed to be non-null
+                    connection.getRoster()
                         .removeRosterListener(contactChangesListener);
+                }
+
                 contactChangesListener = null;
             }
         }
diff --git a/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java b/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
index b664ec24b..d74c07e27 100644
--- a/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
@@ -2433,10 +2433,19 @@ public void checkServerTrusted(X509Certificate[] chain, String authType)
             }
             catch(CertificateException e)
             {
-                fireRegistrationStateChanged(getRegistrationState(),
+                // notify in a separate thread to avoid a deadlock when a
+                // reg state listener accesses a synchronized XMPPConnection
+                // method (like getRoster)
+                new Thread(new Runnable()
+                {
+                    public void run()
+                    {
+                        fireRegistrationStateChanged(getRegistrationState(),
                             RegistrationState.UNREGISTERED,
                             RegistrationStateChangeEvent.REASON_USER_REQUEST,
                             "Not trusted certificate");
+                    }
+                }).start();
                 throw e;
             }