MBP stuck on grey screen

Question

This morning my MBP, mod 6,2 (8GB, 500GB), started acting strange (would not minimize Word, Safari would crash and re-crash on restart...)
so I decided to reboot it. Never came back.
The system sits on the grey screen forever. In many attempts, once or twice it went to the login screen, and after I entered the password, got stuck on that screen removing the cursor.
So far I have:
- booted ML in recovery mode, checked and rechecked the HD (verify disk, check permissions....) - all ok
(recovery mode runs fine, I can browse the web, run disk utility....without any problem)
- reset PRAM and SMC (even if the problem does not appear related)
- booted the AHT disk and passed the brief test (am running the extended one now)
- booted in verbose mode and learned that the system gets stuck in these steps
Com.apple.launchd          1 com.apple.UserEventAgent-LoginWindow                       #          stopping job
Com.apple.launchd          1 com.apple.UserEventAgent-LoginWindow                                #          Sent Job SIGKILL
Com.apple.launchd           1 com.apple.universalaccessd                                           #          stopping job
Com.apple.launchd            1 com.apple.universalaccessd                                                    #          Sent Job SIGKILL
Com.apple.launchd            1 com.apple.helpd                                                               #          stopping job
Com.apple.launchd            1 com.apple.helpd                                                                        #          Sent Job SIGKILL
Com.apple.launchd            1 com.apple.coreservices.appleid.authentication   #          stopping job
where # is the process ID, which keeps increasing. The first time it appears, reads 249, then works its way up constantly.
Any clue on what could be wrong?? I'm mostly interested in backing up the last few days of work before doing anything
drastic with the system, but need to get in the system to do that.
Thanks in advance

Answer 1

If you want to preserve the data on the boot drive, you must try to back up now, before you do anything else. It may or may not be possible. If you don't care about the data, you can skip this step.
There are several ways to back up a Mac that is unable to fully boot. You need an external hard drive to hold the backup data.
1. Boot into Recovery (command-R at startup) or from a local Time Machine backup volume (option key at startup.) Launch Disk Utility and follow the instructions in the support article linked below, under “Instructions for backing up to an external hard disk via Disk Utility.”
How to back up and restore your files
2. If you have access to a working Mac, and both it and the non-working Mac have FireWire or Thunderbolt ports, boot the non-working Mac in target disk mode by holding down the key combination command-T at the startup chime. Connect the two Macs with a FireWire or Thunderbolt cable. The internal drive of the machine running in target mode will mount as an external drive on the other machine. Copy the data to another drive. This technique won't work with USB, Ethernet, Wi-Fi, or Bluetooth.
How to use and troubleshoot FireWire target disk mode
3. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.