diff --git a/EDMarketConnector.py b/EDMarketConnector.py
index 28663e43..7afe5367 100755
--- a/EDMarketConnector.py
+++ b/EDMarketConnector.py
@@ -87,6 +87,9 @@ class AppWindow:
         self.w.rowconfigure(0, weight=1)
         self.w.columnconfigure(0, weight=1)
 
+        self.authdialog = None
+        self.prefsdialog = None
+
         plug.load_plugins(master)
 
         if platform != 'darwin':
@@ -320,6 +323,7 @@ class AppWindow:
 
     # callback after the Preferences dialog is applied
     def postprefs(self, dologin=True):
+        self.prefsdialog = None
         self.set_labels()	# in case language has changed
 
         # (Re-)install hotkey monitoring
@@ -378,7 +382,8 @@ class AppWindow:
             self.session.login(username, config.get_password(username), monitor.is_beta)
             self.status['text'] = ''
         except companion.VerificationRequired:
-            return prefs.AuthenticationDialog(self.w, partial(self.verify, self.login))
+            if not self.authdialog:
+                self.authdialog = prefs.AuthenticationDialog(self.w, partial(self.verify, self.login))
         except companion.ServerError as e:
             self.status['text'] = unicode(e)
         except Exception as e:
@@ -388,6 +393,7 @@ class AppWindow:
 
     # callback after verification code
     def verify(self, callback, code):
+        self.authdialog = None
         try:
             self.session.verify(code)
             config.save()	# Save settings now for use by command-line app
@@ -516,7 +522,8 @@ class AppWindow:
                                 self.status['text'] = ''
 
         except companion.VerificationRequired:
-            return prefs.AuthenticationDialog(self.w, partial(self.verify, self.getandsend))
+            if not self.authdialog:
+                self.authdialog = prefs.AuthenticationDialog(self.w, partial(self.verify, self.getandsend))
 
         # Companion API problem
         except (companion.ServerError, companion.ServerLagging) as e:
@@ -617,8 +624,8 @@ class AppWindow:
                     cmdrs = config.get('cmdrs')
                     cmdrs[0] = monitor.cmdr	# New Cmdr uses same credentials as old
                     config.set('cmdrs', cmdrs)
-                else:
-                    prefs.PreferencesDialog(self.w, self.postprefs)	# First run or failed migration
+                elif not self.prefsdialog:
+                    self.prefsdialog = prefs.PreferencesDialog(self.w, self.postprefs)	# First run or failed migration
 
             if not entry['event'] or not monitor.mode:
                 return	# Startup or in CQC
@@ -726,7 +733,8 @@ class AppWindow:
         try:
             data = self.session.profile()
         except companion.VerificationRequired:
-            return prefs.AuthenticationDialog(self.w, partial(self.verify, self.shipyard_url))
+            if not self.authdialog:
+                self.authdialog = prefs.AuthenticationDialog(self.w, partial(self.verify, self.shipyard_url))
         except companion.ServerError as e:
             self.status['text'] = str(e)
             return
@@ -803,7 +811,8 @@ class AppWindow:
                 with open(f, 'wt') as h:
                     h.write(json.dumps(data, ensure_ascii=False, indent=2, sort_keys=True, separators=(',', ': ')).encode('utf-8'))
         except companion.VerificationRequired:
-            prefs.AuthenticationDialog(self.w, partial(self.verify, self.save_raw))
+            if not self.authdialog:
+                self.authdialog = prefs.AuthenticationDialog(self.w, partial(self.verify, self.save_raw))
         except companion.ServerError as e:
             self.status['text'] = str(e)
         except Exception as e: