Q: Are there known issues in 10.8.5

First of all, many thanks to everyone who suggested ways of dealing with this problem.  As I am now convinced that the problem has been resolved, I'm going to consolidate the relevant information into one post for the convenience of anyone else who runs into this problem.

Background:

I have a MacBook Pro from late 2008, and was running 10.8.4 successfully - i.e., no apparent problems.

I upgraded to 10.8.5, and almost immediately experienced a series of system freezes   In this case "freezing" means that the spinning blue ball goes solid, and neither the magic mouse nor the touchpad respond.  While the freezes seemed to coincide with the upgrade, I obviously could not be certain that it caused the problem.

My MBP would freeze intermittently, with no apparent pattern.  It sometimes froze immediately after I logged in, and it even froze when the only active applications were Finder, Activity Monitor and Little Snitch; all external devices were disconnected during this time.

I'm also the paranoid type, so I had a current Time Machine backup and Install OS X Mountain Lion.App (10.8.4) on a USB drive - just in case.

First Steps:

I did a Command-R restart and used Disk Utility to verify permissions on, and repair the built-in disk; Disk Utility reported that the disk was good, did not need to do any repairs.  (Did this once)

My MBP continued to freeze intermittently, with no apparent pattern.  It sometimes froze immediately after I logged in, and it even froze when the only active applications were Finder, Activity Monitor and Little Snitch; all external devices were disconnected during this time.

I took my MBP to the Genius Bar; they did some testing, checked the logs and experienced a freeze.  The outcome:

• My MBP is "vintage" - very late 2008 model, only just young enough to be considered compatible with OS X 10.8.5, so Apple will not keep it in the store overnight for more intensive testing.  They also don't have spare parts any more.
• The Genius, who was very helpful, expressed the view that it might be the graphics card.  I suspect the hard drive, but the logs do not contain any information that confirms or debunks either theory.  We discussed the idea of reverting from 10.8.5 to 10.8.4, using my Time Machine disk which is current.

Back home I tried to  get the MBP up and running long enough to uninstall PhotoShop CS4 so I could avoid the hassle of calling Adobe to re-enable my license/swhen I re-install them.  After several attempts ended in a freeze, I decided this was a futile effort.

With nothing to lose at this juncture, I decided to re-install 10.8.4 using the USB drive mentioned above.  Miraculously the install ran to completion; that was noteworthy because that process runs far longer than the time between freezes.  I expected the install to wipe the built-in HD, but when it ended I checked, and found all my data files on the HD; the Applications, Downloads and other standard user folders appeared to be intact as well, so the install of 10.8.4 had overwritten the existing copy of 10.8.5.

My MBP has now been up and running almost continuously for almost 48 hours after re-installing 10.8.4; in that time I've copied almost 1TB of data to refresh an external backup drive, updated Time Machine and completed several compute and I/O intensive photographic tasks.  I know this is circumstantial, but I am convinced that re-installing 10.8.4 solved my problem.

If you have this problem, please make sure you have at least one current backup before you attempt what I did.  I'm sure Apple would consider re-installing 10.8.4 on top of 10.8.5 very unorthodox and unsupported, but in my circumstances I'm very pleased with the outcome.

Regards

Lionel