diff --git a/Classes/IncallViewController.m b/Classes/IncallViewController.m
index a5b991804..fd1518bc5 100644
--- a/Classes/IncallViewController.m
+++ b/Classes/IncallViewController.m
@@ -22,7 +22,7 @@
 #import "linphonecore.h"
 #include "LinphoneManager.h"
 #include "private.h"
-#import "ContactPickerDelegate.h"Òß
+#import "ContactPickerDelegate.h"
 
 @implementation IncallViewController
 
diff --git a/Classes/LinphoneAppDelegate.m b/Classes/LinphoneAppDelegate.m
index dcb97b6b7..46c8b1a9b 100644
--- a/Classes/LinphoneAppDelegate.m
+++ b/Classes/LinphoneAppDelegate.m
@@ -42,6 +42,10 @@
 }
 - (void)applicationDidBecomeActive:(UIApplication *)application {
 	[[LinphoneManager instance] becomeActive];
+    
+    if (myPhoneViewController != nil) {
+        [myPhoneViewController updateCallAndBackButtons];
+    }
 }
 
 - (void) loadDefaultSettings {
diff --git a/Classes/LinphoneUI/LinphoneManager.h b/Classes/LinphoneUI/LinphoneManager.h
index 5da93e076..32f403dee 100644
--- a/Classes/LinphoneUI/LinphoneManager.h
+++ b/Classes/LinphoneUI/LinphoneManager.h
@@ -48,6 +48,7 @@ typedef enum _Connectivity {
 }
 +(LinphoneManager*) instance;
 +(LinphoneCore*) getLc;
++(BOOL) audioSessionInterrupted;
 
 -(void) registerLogView:(id<LogView>) view;
 
diff --git a/Classes/LinphoneUI/LinphoneManager.m b/Classes/LinphoneUI/LinphoneManager.m
index de012d74c..75c5dee6e 100644
--- a/Classes/LinphoneUI/LinphoneManager.m
+++ b/Classes/LinphoneUI/LinphoneManager.m
@@ -30,6 +30,7 @@
 
 static LinphoneCore* theLinphoneCore=nil;
 static LinphoneManager* theLinphoneManager=nil;
+static BOOL audioSessionInterrupted = NO;
 
 extern void libmsilbc_init();
 #ifdef HAVE_AMR
@@ -835,6 +836,8 @@ void networkReachabilityCallBack(SCNetworkReachabilityRef target, SCNetworkReach
 }
 
 -(void) beginInterruption {
+    audioSessionInterrupted = YES;
+    
     LinphoneCall* c = linphone_core_get_current_call(theLinphoneCore);
     ms_message("Sound interruption detected!");
     if (c) {
@@ -850,7 +853,12 @@ void networkReachabilityCallBack(SCNetworkReachabilityRef target, SCNetworkReach
         ms_message("Auto resuming call");
         linphone_core_resume_call(theLinphoneCore, (LinphoneCall*) c->data);
     }
-    
+ 
+    audioSessionInterrupted = NO;
+}
+
++(BOOL) audioSessionInterrupted {
+    return audioSessionInterrupted;
 }
 
 
diff --git a/Classes/PhoneViewController.h b/Classes/PhoneViewController.h
index b9f5f09e2..03947ff5c 100644
--- a/Classes/PhoneViewController.h
+++ b/Classes/PhoneViewController.h
@@ -64,6 +64,8 @@
 	IncallViewController* mIncallViewController;
 }
 
+-(void) updateCallAndBackButtons;
+
 @property (nonatomic, retain) IBOutlet UIView* dialerView;
 
 @property (nonatomic, retain) IBOutlet UITextField* address;
diff --git a/Classes/PhoneViewController.m b/Classes/PhoneViewController.m
index 1e06fbf61..26c44d9ce 100644
--- a/Classes/PhoneViewController.m
+++ b/Classes/PhoneViewController.m
@@ -164,6 +164,12 @@
                    [exc.name cStringUsingEncoding:[NSString defaultCStringEncoding]], 
                    [exc.reason cStringUsingEncoding:[NSString defaultCStringEncoding]]);
     }
+    
+    /* if audio session is unavailable -> disable call buttons */
+    if ([LinphoneManager audioSessionInterrupted]) {
+        [callShort setEnabled:NO];
+        [callLarge setEnabled:NO];
+    }
 }
 
 -(void)viewWillAppear:(BOOL)animated {
@@ -212,7 +218,13 @@
 
 
 -(void) displayIncomingCall:(LinphoneCall*) call NotificationFromUI:(UIViewController*) viewCtrl forUser:(NSString*) username withDisplayName:(NSString*) displayName {
-	
+    if ([LinphoneManager audioSessionInterrupted]) {
+        // TODO: should we notify the user and let him cancel the call (without letting him accept it) ?
+        ms_message("Call refused: audio session is not available");
+        linphone_core_terminate_call([LinphoneManager getLc], call);
+        return;
+    }
+    
 	if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)] 
 		&& [UIApplication sharedApplication].applicationState !=  UIApplicationStateActive) {
 		// Create a new notification
@@ -233,17 +245,16 @@
         cd.delegate = self;
         cd.call = call;
         
-		mIncomingCallActionSheet = [[UIActionSheet alloc] initWithTitle:[NSString  stringWithFormat:NSLocalizedString(@" %@ is calling you",nil),[displayName length]>0?displayName:username]
-															   delegate:cd 
-													  cancelButtonTitle:NSLocalizedString(@"Decline",nil) 
+        mIncomingCallActionSheet = [[UIActionSheet alloc] initWithTitle:[NSString  stringWithFormat:NSLocalizedString(@" %@ is calling you",nil),[displayName length]>0?displayName:username]
+                                                            delegate:cd 
+                                                    cancelButtonTitle:NSLocalizedString(@"Decline",nil) 
 												 destructiveButtonTitle:NSLocalizedString(@"Answer",nil) 
-													  otherButtonTitles:nil];
-        
+                                            otherButtonTitles:nil];
+    
 		mIncomingCallActionSheet.actionSheetStyle = UIActionSheetStyleDefault;
 		[mIncomingCallActionSheet showInView:self.parentViewController.view];
 		[mIncomingCallActionSheet release];
 	}
-	
 }
 
 -(void) backToCallViewPressed {
@@ -292,7 +303,7 @@
 
 - (void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex withUserDatas:(void *)datas{
     LinphoneCall* call = (LinphoneCall*)datas;
-	if (buttonIndex == 0 ) {
+	if (buttonIndex == actionSheet.destructiveButtonIndex  ) {
 		linphone_core_accept_call([LinphoneManager getLc],call);	
 	} else {
 		linphone_core_terminate_call ([LinphoneManager getLc], call);
diff --git a/submodules/externals/exosip b/submodules/externals/exosip
index c3da03035..f28804413 160000
--- a/submodules/externals/exosip
+++ b/submodules/externals/exosip
@@ -1 +1 @@
-Subproject commit c3da0303519ad3120355cb85baee9cf6d0e4d1c2
+Subproject commit f288044136b3e60baf6c0805e8cf87e5cdbc7890