Can't boot after 10.8.3 update
My MacPro has worked fine since I upgraded from 10.6.8 to 10.8.1. However, I have not had any success with 10.8.2 or 10.8.3 updates. After installing the update, the computer statrts to boot but stops at the grey screen with the Apple in the center. It does not show the rotating circular image to indicate any activity, just the Apple. It does not matter how long I wait, the boot does not complete. When I boot from 10.8.1 everything works fine again.
Hardware Overview:
Model Name: Mac Pro
Model Identifier: MacPro3,1
Processor Name: Quad-Core Intel Xeon
Processor Speed: 2.8 GHz
Number of Processors: 2
Total Number of Cores: 8
L2 Cache (per Processor): 12 MB
Memory: 10 GB
Bus Speed: 1.6 GHz
Boot ROM Version: MP31.006C.B05
SMC Version (system): 1.25f4
Serial Number (system): Not Available
NVIDIA GeForce GT 120:
Chipset Model: NVIDIA GeForce GT 120
Type: GPU
Bus: PCIe
Slot: Slot-1
PCIe Lane Width: x16
VRAM (Total): 512 MB
Vendor: NVIDIA (0x10de)
Device ID: 0x0640
Revision ID: 0x00a1
ROM Revision: 3386
Any ideas about what would prevent the Mountain Lion updates from booting?
Mac Pro, OS X Mountain Lion (10.8.3), NVIDIA GeForce GT 120