Index: /trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java	(revision 8938)
+++ /trunk/src/org/openstreetmap/josm/gui/progress/PleaseWaitProgressMonitor.java	(revision 8939)
@@ -174,4 +174,7 @@
             public void run() {
                 Main.currentProgressMonitor = PleaseWaitProgressMonitor.this;
+                if (GraphicsEnvironment.isHeadless()) {
+                    return;
+                }
                 if (dialogParent != null && dialog == null) {
                     dialog = new PleaseWaitDialog(dialogParent);
Index: /trunk/src/org/openstreetmap/josm/plugins/PluginHandler.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/plugins/PluginHandler.java	(revision 8938)
+++ /trunk/src/org/openstreetmap/josm/plugins/PluginHandler.java	(revision 8939)
@@ -8,4 +8,5 @@
 import java.awt.Component;
 import java.awt.Font;
+import java.awt.GraphicsEnvironment;
 import java.awt.GridBagConstraints;
 import java.awt.GridBagLayout;
@@ -1099,14 +1100,17 @@
                 )
         };
-        int ret = HelpAwareOptionPane.showOptionDialog(
-                parent,
-                reason,
-                tr("Disable plugin"),
-                JOptionPane.WARNING_MESSAGE,
-                null,
-                options,
-                options[0],
-                null // FIXME: add help topic
-        );
+        int ret = -1;
+        if (!GraphicsEnvironment.isHeadless()) {
+            ret = HelpAwareOptionPane.showOptionDialog(
+                    parent,
+                    reason,
+                    tr("Disable plugin"),
+                    JOptionPane.WARNING_MESSAGE,
+                    null,
+                    options,
+                    options[0],
+                    null // FIXME: add help topic
+            );
+        }
         return ret == 0;
     }
Index: /trunk/src/org/openstreetmap/josm/tools/PlatformHookUnixoid.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/tools/PlatformHookUnixoid.java	(revision 8938)
+++ /trunk/src/org/openstreetmap/josm/tools/PlatformHookUnixoid.java	(revision 8939)
@@ -392,5 +392,7 @@
 
     protected void askUpdateJava(String version) {
-        askUpdateJava(version, "https://www.java.com/download");
+        if (!GraphicsEnvironment.isHeadless()) {
+            askUpdateJava(version, "https://www.java.com/download");
+        }
     }