Thanks EddyMac. You got me thinking, then I had a look and realised I did not do the following step after rebuilding Yosemite
http://www.tonymacx86.com/yosemite-...-os-x-yosemite-using-unibeast-multibeast.html
In case anyone else has the same problem, here are the steps from the link above. If you rebuild Yosemite, you need to run these steps again! Which was the mistake I made, phew, sorted! After doing the steps below, all is good with the world.
after upgrading to Yosemite I got the following error
can't find /mach_kernel
The problem was I did not follow the correct upgrade process (as outlined in the link above). I spent ages messing around trying to sort out why the system was not booting up properly.
I ended up just booting from the unibeast usb drive. This worked, but was a hassle as I had to bring up the bios boot drives every time I turned on my machine.
I deleted the two lines of code, ran multibeast 7, loaded up Chimera 4.0.1 and it worked.
All the steps to upgrade to Yosemite are in the link above, have cut and paste below as well.
Machine.
##############
Save all of your settings, files, apps, etc... by following this simple guide to upgrade OS X Mavericks to OS X Yosemite.
1. Boot OS X Mavericks
2. Remove /Extra/modules/FileNVRAM.dylib if present
3. Remove /System/Library/Extensions/GenericUSBXHCI.kext if present
4. Edit /Extra/org.chameleon.Boot.plist to remove the following 2 lines if present:
5. Create a bootable USB using UniBeast 5
6. Boot from USB and install OS X Yosemite over your existing Mavericks installation
7. Reboot from the USB and choose your existing drive
8. Run MultiBeast 7 and select the following options, and any system-specific Audio and Network drivers.