diff --git a/daemon/core/gui/app.py b/daemon/core/gui/app.py
index d7754b90..eddb60d3 100644
--- a/daemon/core/gui/app.py
+++ b/daemon/core/gui/app.py
@@ -1,7 +1,7 @@
 import logging
 import math
 import tkinter as tk
-from tkinter import PhotoImage, font, ttk
+from tkinter import PhotoImage, font, messagebox, ttk
 from tkinter.ttk import Progressbar
 from typing import Any, Dict, Optional, Type
 
@@ -168,17 +168,30 @@ class Application(ttk.Frame):
     def hide_info(self) -> None:
         self.infobar.grid_forget()
 
-    def show_grpc_exception(self, title: str, e: grpc.RpcError) -> None:
+    def show_grpc_exception(
+        self, message: str, e: grpc.RpcError, blocking: bool = False
+    ) -> None:
         logging.exception("app grpc exception", exc_info=e)
-        message = e.details()
-        self.show_error(title, message)
+        dialog = ErrorDialog(self, "GRPC Exception", message, e.details())
+        if blocking:
+            dialog.show()
+        else:
+            self.after(0, lambda: dialog.show())
 
-    def show_exception(self, title: str, e: Exception) -> None:
+    def show_exception(self, message: str, e: Exception) -> None:
         logging.exception("app exception", exc_info=e)
-        self.show_error(title, str(e))
+        self.after(
+            0, lambda: ErrorDialog(self, "App Exception", message, str(e)).show()
+        )
 
-    def show_error(self, title: str, message: str) -> None:
-        self.after(0, lambda: ErrorDialog(self, title, message).show())
+    def show_exception_data(self, title: str, message: str, details: str) -> None:
+        self.after(0, lambda: ErrorDialog(self, title, message, details).show())
+
+    def show_error(self, title: str, message: str, blocking: bool = False) -> None:
+        if blocking:
+            messagebox.showerror(title, message, parent=self)
+        else:
+            self.after(0, lambda: messagebox.showerror(title, message, parent=self))
 
     def on_closing(self) -> None:
         if self.toolbar.picker:
diff --git a/daemon/core/gui/coreclient.py b/daemon/core/gui/coreclient.py
index c3f48751..d2f0cb87 100644
--- a/daemon/core/gui/coreclient.py
+++ b/daemon/core/gui/coreclient.py
@@ -41,7 +41,6 @@ from core.api.grpc.wrappers import (
 from core.gui import nodeutils as nutils
 from core.gui.appconfig import XMLS_PATH, CoreServer, Observer
 from core.gui.dialogs.emaneinstall import EmaneInstallDialog
-from core.gui.dialogs.error import ErrorDialog
 from core.gui.dialogs.mobilityplayer import MobilityPlayer
 from core.gui.dialogs.sessions import SessionsDialog
 from core.gui.graph.edges import CanvasEdge
@@ -418,10 +417,11 @@ class CoreClient:
             if session_id:
                 session_ids = set(x.id for x in sessions)
                 if session_id not in session_ids:
-                    dialog = ErrorDialog(
-                        self.app, "Join Session Error", f"{session_id} does not exist"
+                    self.app.show_error(
+                        "Join Session Error",
+                        f"{session_id} does not exist",
+                        blocking=True,
                     )
-                    dialog.show()
                     self.app.close()
                 else:
                     self.join_session(session_id)
@@ -433,8 +433,7 @@ class CoreClient:
                     dialog.show()
         except grpc.RpcError as e:
             logging.exception("core setup error")
-            dialog = ErrorDialog(self.app, "Setup Error", e.details())
-            dialog.show()
+            self.app.show_grpc_exception("Setup Error", e, blocking=True)
             self.app.close()
 
     def edit_node(self, core_node: Node) -> None:
diff --git a/daemon/core/gui/dialogs/error.py b/daemon/core/gui/dialogs/error.py
index 731564ec..726f8617 100644
--- a/daemon/core/gui/dialogs/error.py
+++ b/daemon/core/gui/dialogs/error.py
@@ -13,9 +13,11 @@ if TYPE_CHECKING:
 
 
 class ErrorDialog(Dialog):
-    def __init__(self, app: "Application", title: str, details: str) -> None:
-        super().__init__(app, "CORE Exception")
-        self.title: str = title
+    def __init__(
+        self, app: "Application", title: str, message: str, details: str
+    ) -> None:
+        super().__init__(app, title)
+        self.message: str = message
         self.details: str = details
         self.error_message: Optional[CodeText] = None
         self.draw()
@@ -25,13 +27,13 @@ class ErrorDialog(Dialog):
         self.top.rowconfigure(1, weight=1)
         image = images.from_enum(ImageEnum.ERROR, width=images.ERROR_SIZE)
         label = ttk.Label(
-            self.top, text=self.title, image=image, compound=tk.LEFT, anchor=tk.CENTER
+            self.top, text=self.message, image=image, compound=tk.LEFT, anchor=tk.CENTER
         )
         label.image = image
-        label.grid(sticky=tk.EW, pady=PADY)
+        label.grid(sticky=tk.W, pady=PADY)
         self.error_message = CodeText(self.top)
         self.error_message.text.insert("1.0", self.details)
         self.error_message.text.config(state=tk.DISABLED)
-        self.error_message.grid(sticky=tk.NSEW, pady=PADY)
+        self.error_message.grid(sticky=tk.EW, pady=PADY)
         button = ttk.Button(self.top, text="Close", command=lambda: self.destroy())
         button.grid(sticky=tk.EW)
diff --git a/daemon/core/gui/toolbar.py b/daemon/core/gui/toolbar.py
index 1e3e69a5..844a68f2 100644
--- a/daemon/core/gui/toolbar.py
+++ b/daemon/core/gui/toolbar.py
@@ -310,7 +310,9 @@ class Toolbar(ttk.Frame):
             enable_buttons(self.design_frame, enabled=True)
             if exceptions:
                 message = "\n".join(exceptions)
-                self.app.show_error("Start Session Error", message)
+                self.app.show_exception_data(
+                    "Start Exception", "Session failed to start", message
+                )
 
     def set_runtime(self) -> None:
         enable_buttons(self.runtime_frame, enabled=True)