diff --git a/importexport/inc/class.importexport_schedule_ui.inc.php b/importexport/inc/class.importexport_schedule_ui.inc.php
index ef294ce27f..8c0e3930da 100644
--- a/importexport/inc/class.importexport_schedule_ui.inc.php
+++ b/importexport/inc/class.importexport_schedule_ui.inc.php
@@ -363,16 +363,37 @@
 		/**
 		* Execute a scheduled import or export
 		*/
-		public static function exec($data) {
+		public static function exec($data)
+		{
 			ob_start();
 
-			
 			$data['record_count'] = 0;
 			unset($data['errors']);
 			unset($data['warnings']);
 			unset($data['result']);
+
+			if($data['lock'])
+			{
+				// Lock expires
+				if($data['lock'] < time())
+				{
+					unset($data['lock']);
+					$data['warnings'][][] = lang('Lock expired on previous run');
+				}
+				else
+				{
+					// Still running
+					ob_end_flush();
+					return;
+				}
+			}
+
 			$data['last_run'] = time();
 
+			// Lock job for an hour to prevent multiples overlapping
+			$data['lock'] = time() + 3600;
+			self::update_job($data, true);
+			
 			// check file
 			$file_check = self::check_target($data);
 			if($file_check !== true) {
@@ -380,6 +401,7 @@
 				// Update job with results
 				self::update_job($data);
 
+				ob_end_flush();
 				fwrite(STDERR,'importexport_schedule: ' . date('c') . ": $file_check \n");
 				return;
 			}
@@ -438,6 +460,10 @@
 
 			foreach($targets as $target)
 			{
+				// Update lock timeout
+				$data['lock'] = time() + 3600;
+				self::update_job($data, true);
+
 				$resource = null;
 				try {
 					if($resource = @fopen( $target, $data['type'] == 'import' ? 'rb' : 'wb' )) {
@@ -506,7 +532,10 @@
 			}
 
 			// Run time in minutes
-			$data['run_time'] = (time() - $data['last_run']) / 60;
+			$data['run_time'] = round((time() - $data['last_run']) / 60,1);
+
+			// Clear lock
+			$data['lock'] = 0;
 
 			// Update job with results
 			self::update_job($data);
@@ -526,7 +555,7 @@
 		 * Update the async job with current status, and send a notification
 		 * to user if there were any errors.
 		 */
-		private static function update_job($data) {
+		private static function update_job($data, $no_notification = false) {
 			$id = self::generate_id($data);
 			$async = ExecMethod('phpgwapi.asyncservice.read', $id);
 			$async = $async[$id];
@@ -539,6 +568,7 @@
 					$data
 				);
 			}
+			if($no_notification) return $result;
 
 			// Send notification to user
 			if($data['warnings'] || $data['errors'])