Major Photoshop Lag - 2013 MacPro

Question

Having some major Photoshop problems, and this is a BRAND NEW computer, just put into production...
I'm using Photoshop CC 2014. 
Initially, everything works great.  However, after working for about 30 min to 1 hour, or retouching about 15-20 images, the clone tool preview starts lagging heavily.  The tool itself moves fine, but the preview only appears when I stop movement of the tool.  It doesn't do this initially.  Also, when this starts happening, just moving a small layer around also lags.  It doesn't matter what size the file is either. The only way to fix it is to reset my preferences.  However, after a short amount of time, it does it again.
Here is a list of things that I have tried but hasn't fixed the problem:
Disabled plugins.
Made sure my tablet driver was up to date.
Closed Photoshop and use Memory Clean to free up memory.
Rebooted Mac.
Did a hard reset on the Mac as well as cleared PRAM.
Ran the Apple Hardware Test (had no errors).
Unplugged any extra peripherals (wacom tablet, extra monitor, all external hard drives)
Uninstalled Photoshop CC 2014 and used the cleaner tool from Adobe to remove all files.
Adobe tech support had me make a new Mac admin account.Adobe tech also had me log in to root and try.Adobe tech checked my Photoshop settings, cache levels, graphics card settings etc.
Disabled any fonts other than system fonts.
Downloaded and installed older Photoshop CC version. (no extra brushes, plug-ins, actions etc. were installed).
Worked off of one monitor with minimal palettes open.
I feel like after trying all this stuff, it's definitely a bug in the program.
The KEY test here is the following:
I even sent my preferences file to a friend who also has a 2013 Mac Pro.  When he uses my preferences file, his does the EXACT same thing.  However, the difference being, when he goes back to his old preferences file, the problem doesn't come back  like mine.
Again, I have tried Photoshop CC 2014 AND CC without any plug ins, extra brushes, actions, styles, shortcuts, etc. and it still does it.
I'm running a 2013 Mac Pro Quad 37 GHz CPU, which has dual Firepro D300's with 2GB video ram,  and 12GB of 1866MHz DDR3 RAM.  Mac was purchased brand new. OS is Yosemite 10.10.2
here's a video showing the exact problem... (working even on a low resolution .jpg which should be blinding fast)
http://youtu.be/IbOr-_30P5k
Adobe is trying to help, but getting nowhere, and this IS a problem, it's a brand new machine with a brand new install of the OS, and a fresh new user account, and a fresh install of CC2014, this should not be happening.
By simple process of elimination tests, this cannot be a hardware error or an OS error or anything of that nature, otherwise it would not replicate the problem on a friend's MacPro who I send my prefs file to... the fact that the prefs file replicates the problem, PROVES it's a problem with the adobe software. and a solution must be out there?
Thanks in advance for any help.

Answer 1

Thank you for the reply, I appreciate it.
Now, interesting thing is, I know of two other Macpro's one 2013, and one an older quad-core macpro 4,1 both running 10.10.2 and neither of those have this issue?
and the other confusing part to me about this, is why would friend's 2013 Macpro NOT have this issue until using THIS prefs file, if it was an Apple thing?
thanks for your help!
Bill