Mac Pro freeze problems

Question

I have had numerous discussios with Apple Support, the last one concluding I needed to send my computer in for a complete diagnosis and repair. The repair was to replace the logic board upgrading it to a newer version (2.3 GH INTEL CORE I7). On its return occasional crashing continued. I am running OS X 6.7.2. An  firmware upgrade was installed and one crash/freeze occurred at 2:AM Friday Nov 11, which was exaclly to time Time Machine was to update. I found this by going to Applications/Utilities/Console and this indicated my problem might be related to either a software or hardware issue with Time Machine. It has been unplugged since and the computer has run flawlessly. Although Disc utilities gave the external drive a clean bill of health, I am skeptical, since the pocket drive has twice fallen to the floor.
I will ypdate in a week.

Answer 1

Get a new system SSD boot drive. Do a clean install. Be careful what you import. SSD will give your system some juice.
Clone your system with Carbon Copy Cloner and enable the hidden advanced preference option - custom clone feature - to do a checksum on all files copied.
From your description, you should be doing both a SAFE BOOT and Recovery Mode to Repair Disk to fix the disk directory. Zap the PRAM from cold start and reset the STARTUP DISK setting.
I would not trust or rely on that drive and system as is for now.
Another, never use an unstable drive to install, or write to, should be using a backup spare system at this point.
Co clone it to SSD with CCC - after using DU and Safe Boot, and uninstalling any "non-essential" 3rd party app or background process and utilities. Lean, mean, stable and faster performance without the extras.
CS6: I would go for more RAM . FBDIMMs are downright affordable, look for NEMIX on Amazon while looking for Samsung 850 or Samsung XP941. Two: one for system, one for scratch, would be ideal. An EVGA 960 GTX to provide CUDA to CS6 maybe later or 970, more VRAM  the better.