--- validation_api.module	Wed Dec 03 21:05:02 2008
+++ validation_api.module	Wed Dec 03 21:05:02 2008
@@ -556,17 +556,19 @@
       break;
       case 'regex':
         // Make argument change, if applicable, in regex code.
+        $rule = $validator->rule;
         if (count($arguments) > 0) {
           foreach ($arguments as $delta => $argument) {
-            $validator->rule = str_replace('%arguments['. $delta .']', $argument, $validator->rule);
+            $replace['%arguments['. $delta .']'] = $argument;
           }
+          $rule = str_replace(array_keys($replace), array_values($replace), $rule);
         }
 
         // Run the regular expression validation.
-        if (!preg_match($validator->rule, $value)) {
+        if (!preg_match($rule, $value)) {
           $message = $validation_api_field->message;
           // Set up the substitution strings for the message.
           $substitutes['%field'] = $element['#name'];