--- modules/update/update.compare.inc.~1.2.~	2008-01-10 09:56:14.000000000 -0800
+++ modules/update/update.compare.inc	2008-01-14 18:42:30.000000000 -0800
@@ -328,6 +328,9 @@ function update_calculate_project_data($
         $projects[$project]['reason'] = t('No available releases found');
         continue;
       }
+      // Make sure we find the currently installed release, or we know our
+      // available update data is stale.
+      $found_current_release = FALSE;
       foreach ($available[$project]['releases'] as $version => $release) {
         // First, if this is the existing release, check a few conditions.
         if ($projects[$project]['existing_version'] == $version) {
@@ -358,6 +361,7 @@ function update_calculate_project_data($
               'data' => t('Your currently installed release is now unsupported, and is no longer available for download. Disabling everything included in this release or upgrading is strongly recommended!'),
             );
           }
+          $found_current_release = TRUE;
         }
 
         // Otherwise, ignore unpublished, insecure, or unsupported releases.
@@ -418,7 +422,7 @@ function update_calculate_project_data($
         }
 
         // Stop searching once we hit the currently installed version.
-        if ($projects[$project]['existing_version'] == $version) {
+        if ($found_current_release) {
           break;
         }
 
@@ -446,6 +450,26 @@ function update_calculate_project_data($
         }
       }
 
+      // If we were unable to find the currently installed release, we
+      // have bogus (probably just stale) available update data.
+      if (!$found_current_release) {
+        $projects[$project]['status'] = UPDATE_UNKNOWN;
+        $projects[$project]['reason'] = t('Current release not found');
+        $projects[$project]['extra'][] = array(
+          'class' => 'release-not-found',
+          'label' => t('Unknown release'),
+          'data' => t('The currently installed version of this project was not found in the list of available updates.'),
+        );
+        // Unset everything we thought we knew about this, since it's bogus.
+        unset($projects[$project]['recommended']);
+        unset($projects[$project]['security updates']);
+        unset($projects[$project]['also']);
+        unset($projects[$project]['dev_version']);
+        unset($projects[$project]['latest_version']);
+        // TODO: clear the available update cache, too?
+        continue;
+      }
+
       // If we were unable to find a recommended version, then make the latest
       // version the recommended version if possible.
       if (!isset($available[$project]['recommended']) && isset($available[$project]['latest_version'])) {