I have a WPMU network installation and the past days

I have a WPMU network installation and the past days i'm redesigning the theme and the website. I've installaded revSlider to create some stunning sliders but the plugin doesnt let me "save" any slider i try to create.
I've removed it and reinstalled it and nothing. same errors.
Tried importing a revslider via the funtion import it has, it imported it and again doesnt let me edit it.
Can you help me with this?
Website is in coming soon mode, so nothing is displayed outside.
error messages i get are:

Warning: array_key_exists() expects parameter 2 to be array, null given in /home/easyonline/public_html/wp-content/plugins/revslider/inc_php/revslider_operations.class.php on line 1330

Warning: array_key_exists() expects parameter 2 to be array, null given in /home/easyonline/public_html/wp-content/plugins/revslider/inc_php/revslider_operations.class.php on line 1330
{"success":false,"message":"Field title</b> should not be empty"}

Can someone help me with this?
Thank you in advance