MacBook Pro Retina Gray Screen after double boot

Hello,

I have got a problem that I can not handle myself. I followed the instructions of installing dual boot with REFIND on OS X. Everything went smooth until an error at the end of Kali installation due to network card driver. I decided to look for a solution online, so I canceled the installation in order to get back to OS X and find an answer. After reboot, I can hear the initial Mac sound, but nothing appears on the screen. Yes, i have tried to run recovery / reset PRAM / boot menu options, but nothing works, the grey screen persists. For the record, I have partitioned 30GB on SSD disk while still on Mac. Then I converted that partition into ext1/swap disk during Kali installation. I guess either that, or REFIND is the reason of the problem. If You have any suggestions, I will test them as we go.

Thank You in advance,

BilusMX