New Install Error Notice: The called constructor method for WP_Widget in core_w

I installed the theme on a test set with no problems. I then downloaded it to the live site which is on the same server so all the same settings and versions. On the live site I have the above error. I have deactivated all the plugins but the error is still there

Anyone shed any light?

All fixed now – had debug mode on

Thanks for sharing Kairen