Photoshop CS5 64 bit crashes at launch, save as, and when opening photos from Lightroom.

Question

I have had this problem intermittently for years with different versions and different computers, but this time it is not going away.  I need to use the 64 bit version for large files, but it keeps crashing in several different ways.
1- I open the program from the desktop.  It shows the spash screen, shows the workspace for a couple of seconds, and then crashes with the message:
Problem Event Name:
APPCRASH
  Application Name:
Photoshop.exe
  Application Version:
12.1.0.0
  Application Timestamp:
4d90d339
  Fault Module Name:
StackHash_8d67
  Fault Module Version:
0.0.0.0
  Fault Module Timestamp:
00000000
  Exception Code:
c0000096
  Exception Offset:
0000000078e650ac
  OS Version:
6.1.7601.2.1.0.256.48
  Locale ID:
1033
  Additional Information 1:
8d67
  Additional Information 2:
8d672743ada8a2e1e75c51ac7051c8c2
  Additional Information 3:
354b
  Additional Information 4:
354bf194360e47150cf5d5ca4e71d674
I am using the latest version.
My video card drivers are totally up to date.
I am using a decent computer with 16 gig of ram.
I am opening the program as an administrator.
I have reset the prefrences too many times to count by deleting the prefrences and holding down ctrl+alt+shift at startup.
2- If by some wild stretch of the imagination I get the program to start with totally cleared prefrences and running as administrator then the program will crash about 75% of the time when using "Save As".
If I try to do anything special like create a new folder to put the file into then the chances of a crash increase greatly.
3- If I try to open up a file from Lightroom, even if the files are opening every other way, Photoshop will crash very often.
What is going on here?  I have made no changes to my computer, have not installed any new programs, and, as I stated earlier, have everything updated.  I even stopped using plugins a long time ago because I did not want to take the chance that it was going to cause this fragile program to crash, so all plugins are uninstalled.  Why does this keep happening?  When this has happened before everything will work fine for months and then suddenly I cannot get the program to open.  When it does open again, for seemingly as unknown a reason as when it stopped, it will work anywhere from a few minutes to another couple of months.
This seems to be a problem that tons of people have, but I have not been able to find any answer other than "Delete Settings" or "Run as Administrator" or "Update *****." 
What can I do to keep this from happening and to fix it when it happens?

Answer 1

Update - Problem Solved.
The problem turned out to be with with Avast.  I found other people that were having the same problem with Outlook and they pointed to this problem.  The live scripts protection seems to have been causing the crash on startup.  Why it was intermittant at first and got worse I have no idea, but since disabling Avast temporarily while starting I have not had the problem again.  Now I am just going to have to start shopping for more Photoshop friendly antivirus software.
Thank you for the advice Mylenium, unfortunately (or actually fortunately for me) I did not have any 64 bit conflicts.
The other action that I took was to remove all programs installed since the problem started.  This did not fix the problem but it certainly cannot hurt to keep everything that I am not using off the computer anyways.