Mac issues: grey screen, cannot reinstall mac os from recover, unapproved caller Well, the past few days have been a near disaster. This whole problem started when I was using Chrome and I suddenly couldn't access pages. I checked Safari, and it wasn't working either. Since I was getting the "Oh snap!" page from Chrome, I X'd it out and tried to reopen it. Chrome's dock icon would just bounce once (usually it bounces until it opens) without opening. I tried to restart the computer, but the "Restart" and "Shut Down" buttons on the Apple Menu weren't working, so I held down the power button and did a force shutdown. When I tried to turn the MacBook back on, I was stuck in the grey screen forever. I have tried everything on the Apple troubleshooting pages. I tried Safe Mode and I was still stuck on the grey screen. I tried the Safe Mode showing progress, and for some reason I could get back in, but then the cycle began anew with Chrome not working.

I tried the PRAM reset or whatever it's called. 

I finally tried to do a Mac OS X from the recovery. Sometimes it won't let me start the reinstall and other times it gets to like 6 minutes remaining and then it will suddenly stop. 

Edit: I forgot to mention that I did all the verify disk and permissions and repairs in the Disk Utility in the recovery. I also ran the Apple Hardware Test, and it said nothing was wrong. At times when the computer was able to boot but having troubles I was getting an "unapproved caller" message.
In case anyone is interested, I took the Mac to the Apple Store and the issue was the Mac hard drive cable. They replaced it and it works fine now.