[Q] Installing ROM's to P930? topic

So what I am wanting to do, is flash a custom ROM to the phone, It's rooted, I have CWM installed, I have the gapps and a few roms I want to test out. But every time I go to flash, they come out to be successful, yet when I reboot my phone, it takes me into the recovery for the device and says:

Code:

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Secure booting Error!
Cause: boot certification verify

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Enter the fastboot...
Enter the fastboot...

Long time no see!
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I really don't understand what i am doing wrong. Do I need to unlock the OEM, do I need to flash some type of custom kernel? I really don't understand how I have the hardest time with the installation of this phone, yet everyone else can get it spot on. I have been trying to do this for some time but there has been no luck on installing the roms. Any and all assistance would be GREATLY appreciated.