diff --git a/SourceGen/AppForms/ProjectView.cs b/SourceGen/AppForms/ProjectView.cs
index 89aa253..2b3c8d1 100644
--- a/SourceGen/AppForms/ProjectView.cs
+++ b/SourceGen/AppForms/ProjectView.cs
@@ -200,15 +200,21 @@ namespace SourceGen.AppForms {
                     Properties.Resources.RUNTIME_DIR_NOT_FOUND_CAPTION,
                     MessageBoxButtons.OK, MessageBoxIcon.Error);
                 Application.Exit();
+                return;
             }
             try {
                 PluginDllCache.PreparePluginDir();
             } catch (Exception ex) {
+                string pluginPath = PluginDllCache.GetPluginDirPath();
+                if (pluginPath == null) {
+                    pluginPath = "<???>";
+                }
                 string msg = string.Format(Properties.Resources.PLUGIN_DIR_FAIL,
-                    PluginDllCache.GetPluginDirPath() + ": " + ex.Message);
+                    pluginPath + ": " + ex.Message);
                 MessageBox.Show(msg, Properties.Resources.PLUGIN_DIR_FAIL_CAPTION,
                     MessageBoxButtons.OK, MessageBoxIcon.Error);
                 Application.Exit();
+                return;
             }
 
             logoPictureBox.ImageLocation = RuntimeDataAccess.GetPathName(LOGO_FILE_NAME);
diff --git a/SourceGen/RuntimeDataAccess.cs b/SourceGen/RuntimeDataAccess.cs
index 1e60ff2..7c0f43c 100644
--- a/SourceGen/RuntimeDataAccess.cs
+++ b/SourceGen/RuntimeDataAccess.cs
@@ -38,7 +38,10 @@ namespace SourceGen {
                 return sBasePath;
             }
 
-            string exeName = Process.GetCurrentProcess().MainModule.FileName;
+            // Process.GetCurrentProcess().MainModule.FileName returns "/usr/bin/mono-sgen"
+            // under Linux, which is not what we want.  Since this class is part of the main
+            // executable, we can use our own assembly location to get the desired answer.
+            string exeName = typeof(RuntimeDataAccess).Assembly.Location;
             string baseDir = Path.GetDirectoryName(exeName);
             if (string.IsNullOrEmpty(baseDir)) {
                 return null;
diff --git a/SourceGen/Sandbox/PluginDllCache.cs b/SourceGen/Sandbox/PluginDllCache.cs
index 8396c8c..93a4ff7 100644
--- a/SourceGen/Sandbox/PluginDllCache.cs
+++ b/SourceGen/Sandbox/PluginDllCache.cs
@@ -63,10 +63,14 @@ namespace SourceGen.Sandbox {
         /// <summary>
         /// Computes the path to the plugin directory.  Does not attempt to verify that it exists.
         /// </summary>
-        /// <returns>Plugin directory path.</returns>
+        /// <returns>Plugin directory path, or null if we can't find the application data
+        ///   area.</returns>
         public static string GetPluginDirPath() {
             if (sPluginDirPath == null) {
                 string runtimeUp = Path.GetDirectoryName(RuntimeDataAccess.GetDirectory());
+                if (runtimeUp == null) {
+                    return null;
+                }
                 sPluginDirPath = Path.Combine(runtimeUp, PLUGIN_DIR_NAME);
             }
             return sPluginDirPath;