My flashed '09 Mac Pro running 10.7.5 went to sleep and failed to wake up. Boot drive is 256 GB OWC SSD and I have a 500GB data drive and a 2TB green drive partitioned as Time Machine drives for boot and data. First I did a hard power down and tried to reboot; got the startup screen and spinning wheel which looked good, but the wheel abruptly stopped after a seemingly too short time and disappeared, leaving me stuck on the grey startup screen with Apple. Moving and clicking the mouse resulted in a spinning ball that never went away. I repeated the process and reset PRAM during startup but same thing happened. I rebooted in safe mode and saw everything seemed to be intact but nothing I tried subsequently fixed the problem: 1)Shut down and restarted from recovery and repaired permissions, verified disk and repaired disk in that order (probably should have been vice versa). 2) Started from DiskWarrior thumb drive and repaired boot drive directory. I note that DW showed only a few minor file problems (like the dreaded incorrect custom icon) and in fact reported directory was well optimized. 3) Booted from Drive Genius 3 DVD and ran diagnostics on directory and files. No problems. Also, in safe mode I opened Time Machine and found it was not set up, but it had been so this might be due to safe mode itself. I have found similar cases on Apple forum with suggested causes as graphics card or SSD problems. Ideas as to what happened, how to troubleshoot or how to fix? I need to get this sick puppy back up asap. ps- I should mention that the machine has been running essentially trouble free for 3 or 4 years in this same basic configuration. Only a relatively few well known programs from the Mac canon have been installed and software updates have been run regularly. No problems noted afterwards.