diff --git a/extension/CRM/Banking/Helpers/Lock.php b/extension/CRM/Banking/Helpers/Lock.php
new file mode 100644
index 00000000..574da286
--- /dev/null
+++ b/extension/CRM/Banking/Helpers/Lock.php
@@ -0,0 +1,36 @@
+<?php
+/*-------------------------------------------------------+
+| Project 60 - CiviBanking                               |
+| Copyright (C) 2013-2014 SYSTOPIA                       |
+| Author: B. Endres (endres -at- systopia.de)            |
+| http://www.systopia.de/                                |
++--------------------------------------------------------+
+| This program is released as free software under the    |
+| Affero GPL license. You can redistribute it and/or     |
+| modify it under the terms of this license which you    |
+| can read by viewing the included agpl.txt or online    |
+| at www.gnu.org/licenses/agpl.html. Removal of this     |
+| copyright header is strictly prohibited without        |
+| written permission from the original author(s).        |
++--------------------------------------------------------*/
+
+/**
+ * Get a batching lock
+ * 
+ * the lock is needed so that only one relevant process can access the 
+ * payment/statment data structures at a time
+ * 
+ * @return lock object. check if it ->isAcquired() before use
+ */
+function banking_helper_getLock($type, $id) {
+  if ($type=='tx') {
+    $timeout = 7.0; // TODO: do we need a setting here?
+    return new CRM_Core_Lock('org.project60.banking.tx'.'-'.$id, $timeout);
+  } elseif ($type=='txbatch') {
+    $timeout = 600.0; // 10mins, TODO: do we need a setting here?
+    return new CRM_Core_Lock('org.project60.banking.txbatch'.'-'.$id, $timeout);    
+  } else {
+    error_log("org.project60.banking - Lock of type '$type' not known.");
+    return NULL;
+  }
+}
diff --git a/extension/CRM/Banking/Matcher/Engine.php b/extension/CRM/Banking/Matcher/Engine.php
index 294e7e4e..75ae4851 100755
--- a/extension/CRM/Banking/Matcher/Engine.php
+++ b/extension/CRM/Banking/Matcher/Engine.php
@@ -25,6 +25,7 @@
  */
 
 require_once 'CRM/Banking/Helpers/OptionValue.php';
+require_once 'CRM/Banking/Helpers/Lock.php';
 
 class CRM_Banking_Matcher_Engine {
   
@@ -90,12 +91,20 @@ private function initPlugins() {
    *                                    This will destroy all records of the execution!
    */
   public function match( CRM_Banking_BAO_BankTransaction $btx, $override_processed = FALSE ) {
+    $lock = banking_helper_getLock('tx', $btx->id);
+    if (!$lock->isAcquired()) {
+      error_log("org.project60.banking - couldn't acquire lock. Timeout is ".$lock->_timeout);
+      return false;
+    }
+
+    error_log("matching ".$btx->id);
     if (!$override_processed) {
       // don't match already executed transactions...
       $processed_status_id = banking_helper_optionvalueid_by_groupname_and_name('civicrm_banking.bank_tx_status', 'Processed');
       $ignored_status_id = banking_helper_optionvalueid_by_groupname_and_name('civicrm_banking.bank_tx_status', 'Ignored');
       if ($btx->status_id == $processed_status_id || $btx->status_id == $ignored_status_id) {
         // will not match already executed transactions
+        $lock->release();
         return true;
       }
     }
@@ -114,11 +123,17 @@ public function match( CRM_Banking_BAO_BankTransaction $btx, $override_processed
         foreach ($plugins as $plugin) {
           // run matchers to generate suggestions
           $continue = $this->matchPlugin( $plugin, $context );
-          if (!$continue) return true;
+          if (!$continue) {
+            $lock->release();
+            return true;
+          }
 
           // check if we can execute the suggestion right aways
           $abort = $this->checkAutoExecute($plugin, $btx);
-          if ($abort) return false;
+          if ($abort) {
+            $lock->release();
+            return false;
+          }
         }
       }
     }    
@@ -129,6 +144,8 @@ public function match( CRM_Banking_BAO_BankTransaction $btx, $override_processed
     $btx->status_id = $newStatus;
     $btx->setStatus($newStatus);
 
+    error_log("done matching ".$btx->id);
+    $lock->release();
     return false;
   }
   
@@ -143,8 +160,17 @@ protected function checkAutoExecute($plugin, $btx) {
       foreach ($suggestions as $suggestion) {
         if ($suggestion->getPluginID()==$plugin->getPluginID()) {
           if ($suggestion->getProbability() >= $plugin->autoExecute()) {
+            $lock = banking_helper_getLock('tx', $btx->id);
+            if (!$lock->isAcquired()) {
+              error_log("org.project60.banking - couldn't acquire lock. Timeout is ".$lock->_timeout);
+              continue;
+            }
+
             $btx->saveSuggestions();
-            return $suggestion->execute( $btx, $plugin );
+            $result = $suggestion->execute( $btx, $plugin );
+
+            $lock->release();
+            return $result;
           }
         }
       }