Index: pathauto.admin.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/pathauto/pathauto.admin.inc,v
retrieving revision 1.10.2.1
diff -u -p -r1.10.2.1 pathauto.admin.inc
--- pathauto.admin.inc	24 Jun 2008 16:07:51 -0000	1.10.2.1
+++ pathauto.admin.inc	9 Jan 2010 21:16:22 -0000
@@ -70,7 +70,7 @@ function pathauto_admin_settings() {
     '#size' => 3,
     '#maxlength' => 3,
     '#default_value' => variable_get('pathauto_max_length', 100),
-    '#description' => t('Maximum length of aliases to generate. 100 is recommended. See <a href="@pathauto-help">Pathauto help</a> for details.', array('@pathauto-help' => url('admin/help/pathauto'))),
+    '#description' => t('Maximum length of aliases to generate. 100 is recommended. The maximum possible length is @max. See <a href="@pathauto-help">Pathauto help</a> for details.', array('@pathauto-help' => url('admin/help/pathauto'), '@max' => _pathauto_get_schema_alias_maxlength())),
   );
 
   $form['general']['pathauto_max_component_length'] = array(
Index: pathauto.inc
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/pathauto/pathauto.inc,v
retrieving revision 1.45.2.6
diff -u -p -r1.45.2.6 pathauto.inc
--- pathauto.inc	3 Dec 2009 16:13:01 -0000	1.45.2.6
+++ pathauto.inc	9 Jan 2010 21:16:22 -0000
@@ -301,7 +301,7 @@ function pathauto_create_alias($module, 
   // Trim any leading or trailing slashes
   $alias = preg_replace('/^\/|\/+$/', '', $alias);
 
-  $maxlength = min(variable_get('pathauto_max_length', 100), 128);
+  $maxlength = min(variable_get('pathauto_max_length', 100), _pathauto_get_schema_alias_maxlength());
   $alias = drupal_substr($alias, 0, $maxlength);
 
   // If the alias already exists, generate a new, hopefully unique, variant
@@ -349,6 +349,17 @@ function pathauto_create_alias($module, 
 }
 
 /**
+ * Fetch the maximum length of the {url_alias}.dst field from the schema.
+ *
+ * @return
+ *   An integer of the maximum url alias length allowed by the database.
+ */
+function _pathauto_get_schema_alias_maxlength() {
+  $schema = drupal_get_schema('url_alias');
+  return $schema['fields']['dst']['length'];
+}
+
+/**
  * Verify if the given path is a valid menu callback.
  *
  * Taken from menu_execute_active_handler().