Exception code 0xc0000005 means "access violation": that code tried to write to memory that it doesn't have access to. This can happen for a whole lot of reasons, and it can be terribly hard to track down the problem.
That you get the error in a "The application failed to start correctly" MessageBox indicates that the exception happens before
the application starts. This could happen for a number of reasons... one would be failing initialization code in one of the DLLs used by the executable, another could be malware or anti-malware (or stuff that uses system hooks or...) programs playing around. Iirc it's also the generic error message you get when trying to run dotNET programs without the framework installed (really should've been a more informative message!), but SSC isn't dotNET.
Because there's so many possible causes, it'll be hard getting anything useful from google searches. FWIW, I used to run 2.56.01 and just upgraded to 2.78.01, and both work on my 64bit Win7 installation.
Are you running any other anti-whatever software besides Symantec? Or an application like AdMuncher? Any "windows enhancers" (virtual desktops, or programs that adds stuff like sticky-windows, minimize-to-tray, window-rollup, ... to all windows)? Anything that sets keyboard/mouse hooks or otherwise injects DLLs into other processes could be potential problems.
You could try monitoring program startup with SysInternals' Process Monitor
, but it's pretty GeekBoyPowerHeadTM
and extremely verbose - akin to looking for a needle in a haystack.