Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 14465)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/MapCSSStyleSource.java	(revision 14466)
@@ -458,4 +458,10 @@
                 Logging.error(e);
                 logError(new ParseException(e.getMessage())); // allow e to be garbage collected, it links to the entire token stream
+            } catch (IllegalArgumentException e1) {
+                final RuntimeException e = new JosmRuntimeException(e1.getMessage());
+                Logging.warn(tr("Failed to parse Mappaint styles from ''{0}''. Error was: {1}", url, e.getMessage()));
+                Logging.error(e);
+                logError(e);
+
             }
             if (metadataOnly) {
Index: trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Selector.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Selector.java	(revision 14465)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/mapcss/Selector.java	(revision 14466)
@@ -4,4 +4,5 @@
 import static org.openstreetmap.josm.data.projection.Ellipsoid.WGS84;
 
+import java.text.MessageFormat;
 import java.util.Collection;
 import java.util.Collections;
@@ -654,5 +655,5 @@
             case "setting": return BASE_SETTING;
             default:
-                throw new IllegalArgumentException("unknown selector " + base);
+                throw new IllegalArgumentException(MessageFormat.format("Unknown MapCSS base selector {0}", base));
             }
         }