you can try this in the interim: boot into your MacBook Pro’s Recovery mode by holding down a Command key and the R key as it starts up. When the Mac OS X Utilities menu appears, select Disk Utility. On the left-hand side of the Disk Utility window, select your internal disk’s boot partition (typically called “Macintosh HD”). On the right-hand side, press the Verify Disk button if it’s not greyed out; if it is greyed out, or if it reports that it found errors, press the Repair Disk button. Once the verification/repair is completed, exit Disk Utility and select Restart from the Apple menu to restart into normal mode. Do you still get the same grey screen + progress bar + beach ball of doom?
If it still not work than visit local authorized repair center.
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