[MBP 5,3 OSX 10.6 Snow Leopard (I think)] I've run into this problem. My machine is pretty much identical to the the one in the link. I did manage to boot into the system once and it said I needed to do a repair disk, which I did via booting through the mac CD which didn't work. If I reinstall OSX how do I protect my files? Also the real kicker is when this started I was about to back up using time machine for the first time in 5/6 months. I copied and pasted this from a topic I made on Reddit, I didn't get any answers and I was told this place is quite good for support. I think I'm going to need to resinstall OSX. I have a back up on time machine from June but if I restore through that I'll loose a lot of stuff over the past few months wont I? Funny thing is it started having these problems on the same day I started looking for my time machine disk since I hadn't backed my files up for a while.