Index: trunk/src/org/openstreetmap/josm/tools/HttpClient.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/HttpClient.java	(revision 14521)
+++ trunk/src/org/openstreetmap/josm/tools/HttpClient.java	(revision 14522)
@@ -161,5 +161,9 @@
                 );
                 if (Logging.isDebugEnabled()) {
-                    Logging.debug("RESPONSE: {0}", connection.getHeaderFields());
+                    try {
+                        Logging.debug("RESPONSE: {0}", connection.getHeaderFields());
+                    } catch (IllegalArgumentException e) {
+                        Logging.warn(e);
+                    }
                 }
                 if (DefaultAuthenticator.getInstance().isEnabled() && connection.getResponseCode() == HttpURLConnection.HTTP_UNAUTHORIZED) {