Hi,
Just bought the component, installed it and it gave me a blank page. I disabled all of the extension entries in the database to get access to the admin panel again. Then started enabling them one at a time until I found which one caused the issue. The problem was the "System - Responsivizer NoToolbar" entry.

I am using Joomla 2.5.28 and installed the "responsivizer_v2.1.1_forjoomla1.6_1.7_2.5.zip" install. I also tried installing locally on JAMP and ran into the same issue.