In this error message, you see that you are using JFTP that means that you have enabled the Joomla FTP Layer.
It seems that you have not correctly setup the FTP Layer as it is not allowed to create directory with your FTP user and password provided to joomla.
Check the FTP parameters in the Global Configuration.
Review also the tutorial video 15 that show how to setup the FTP Layer.
www.jms2win.com/tutorial#jms12x-15
You can test your FTP parameter with an external FTP tool and re-use exactly the same parameter than the one that you have provided to Joomla.
When you have the FTP logged, check that the path you have provided to Joomla is correct and if you can create directory like "tmp"