Thanks for your input, John.  Of course, you have Win 8.  You're very calm and reasonable, as always, while my post was downright ornery (sorry about that).
 
I got on the phone with tech support, and the problem is still not solved.  We went over some settings in configuration and buffers, but basically, the tech suggested that the problem is something in my old project (which was created in X2), since a brand new project worked fine in X2a.  I even tried dumping all the audio from my X2 project into a new X2a project, as he suggested.  However, the problem persists.  This leads me to conclude again that, with my Win 7 x64 system, the patch has introduced a performance issue.  I must reiterate that the same project had no such problems in X2, but they appear in X2a:  long delay after hitting play and record, long delay in rewinding to now marker, long delay in undo recording along with weird auto-scrolling around the project during the delay. 
 
Sure, X2a seems to work fine with a new project with hardly any tracks, but that doesn't get to the performance issue.  This is disheartening.  I have to work, so I'm going back to 8.5.3 (for layers) to track and X1 to mix.  I have to give up on X2, and my future relationship with Sonar is in doubt.  Maybe I'll try X3 or just fork out the big bucks for a new Pro Tools system.

Lol all my students are buying the last x1 produtcion pack here in france (at the price of producer)...with a free upgrade to x2 ....

I m still givingv course under x1 and told all my student to hold on before i say ok .....witch is not now !!!

X2 , as you may have guessed , not installed yet on my system ...

No problems with either X2 or X2a here with W7 64 bit (except one instance of a random crash with X2 after opening Rapture). For me X2a is more solid than X1d was. 

Since upgrading to X2 I started having issues. X1 was solid for me. Issues got worse and worse after the quick fix and a nightmare after X2a. I tried everything I could think of for weeks. After reimaging my pc 3 times with the pc factory image and to no avail of resolution. I bought a copy of Win 7, formatted the drive and installed a clean machine, nothing from the manufacturer. (HP) Installed all my drivers, chipset, MS updates etc. I installed X2 pro, then my plugins. Tested all my projects and she's puring like a kitten right now. Not a glich a click a blip. Knock on wood... I didn't install the quickfix or the X2a patches and won't. If all is working well from here on I will not upgrade or install a single patch. You can have the bells and whistles. I need stability. The only applications I needed to installed on this pc are MS Word, Acrobat 8 pro and  Powerdirector that I use to make videos and my virus software. That's it. I will not install anything else on this pc. There were too many variables to pinpoint the cause of problems but I will advise to dedicate your pc to recording and not use it for anything else if that possible. Fortuanately I have a laptop that I use for mail and other apps.
 
Thanks for listening to my rant. I'm happy again. I can actually record and mix now. Yeah!!!

I upgraded straight from X1d to X2a and noticed a hit in performance too. After playing around I changed the "ThreadSchedulingModel" to 2 even though it's not recommended for dual core systems (I have a Core2Duo Macbook with Windows 7), and it seemed to work a lot better. Now almost all my projects play fine at low latency.