I have just updated yosemite and I get a no entry sign on boot and thats it, it won't start up. I do have a third party hard drive and trim enabled so I tried this. http://www.cindori.org/trim-enabler-and-yosemite/ But it still won't boot. (When i performed the last command kextcache -u "/Volumes/Your Disk name" it went to the next line immediately, no delay, not sure if it ran properly) If anyone has any ideas that would be great. ps If I just do a reinstall OS X from the CMD+R recovery will it keep all my installed apps from OSX and leave my windows bootcamp alone?