I am trying to open a jmx file written with Apache JMeter 2.7 in the last release Apache JMeter 2.11. I am getting this errors log :
2014/09/10 09:29:44 INFO
You're using Third Party jmeter-plugins.org plugins.
You need to add the required jar in lib/ext so that it works.
Download plugins-manager.jar from here and put it into lib/ext directory, then restart JMeter.
Note you need to do it each time you upgrade your jmeter version !
If you're looking to learn jmeter correctly, this book will help you.