Index: src/org/openstreetmap/josm/plugins/PluginInformation.java
===================================================================
--- src/org/openstreetmap/josm/plugins/PluginInformation.java	(revision 155)
+++ src/org/openstreetmap/josm/plugins/PluginInformation.java	(revision 157)
@@ -41,5 +41,5 @@
 		try {
 			ClassLoader loader = URLClassLoader.newInstance(
-					new URL[]{new URL("file://"+file.getAbsolutePath())},
+					new URL[]{new URL(getURLString())},
 					getClass().getClassLoader());
 			Object plugin = Class.forName(className, true, loader).newInstance();
@@ -49,3 +49,9 @@
 		}
 	}
+
+	private String getURLString() {
+		if (System.getProperty("os.name").startsWith("Windows"))
+			return "file:/"+file.getAbsolutePath();
+		return "file://"+file.getAbsolutePath();
+    }
 }