10.7.5 gray screen on startup

I am fairly Mac savvy user. I've tried all reccomended steps to fix the issue, but to no avail:/

Safari was running several windows & tabs when the crash occurred. Now I can safe boot, but it hangs on a blank gray screen instead of launching my desktop.

I updated/reinstalled the OS, nada. I bought a new HDD, used carbon copy cloner, still nothing! Please help, deadlines approaching!

MacPro 3,1