I use Bootcamp for Windows and rEFInd boot loader for Ubuntu 14.04. It used to work fine. Macbook Pro late 2014, came with Yosemite, upgraded to El Capitan.
I was booted into Ubuntu and out of the room. When I came back the screen looked strange, black & smeary, I think my cats walked on the keyboard. Also the fan is racing, but the computer isn't hot.
I rebooted. I had trouble starting Ubuntu, I booted the Mac Recovery Disk, which went straight to Internet Recovery - because the recovery partition is still Yosemite. I made a bootable USB with El Capitan. It doesn't have the Apple Hardware Test tools, and when it starts it says the battery isn't detected, but the battery is working. However, when I connect the charger, the lights don't go on.
Then I was able to boot Ubuntu from rEFInd for a couple of days, but for the past two days I am unable to boot anything except OSX & the recovery drives (one internal, Yosemite, and the USB with El Capitan).
I tried to boot a live USB Boot Repair disk, but it doesn't boot. I can't start Windows either. I can't start any OS except OSX.
I reinstalled rEFInd v 0.10.2. I used the install script in the El Capitan recovery boot because SIP was turned on. I also disabled crsutil in the terminal there.
When I try to boot Ubuntu in recovery mode it hangs at "Loading initial ramdisk" - I added nomodeset to the commands and searched a lot for a solution before posting here. I'm pretty sure that is also why the Boot Repair disk doesn't boot.
I ran a scan with Avast Antivirus.
In the El Capitan boot I tired to restore a previous Time Machine image, but it didn't find any, but I should have a couple since installing El Capitan. I have to restore from that boot because my Recovery HD partition is still Yosemite which came installed.
Another weird symptom is sometimes when I boot OSX wifi is off and I can't turn it on. Then I reboot and it's turned on.
I'm starting to think there is a hardware fault - is there something I am missing? Should I try rolling back to Yosemite? The triple boot was working fine after installing El Capitan, until last week when my cats borked it.